Applications of Derivatives Exam Prep
Full explanation, worked examples & memory tricks in the app
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Full explanation, worked examples & memory tricks in the app
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Show that of all rectangles inscribed in a fixed circle, the square has the maximum area.
The square inscribed in a circle has the maximum area due to symmetry and equal side lengths.
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Find the interval in which 2x^3 + 2x^2 + 12x - 1 is strictly increasing.
The function is strictly increasing where its derivative is positive.
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Find positive number whose sum is 16 and the sum of whose cubes is minimum.
The numbers are 8 and 8.
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Find the intervals in which the function f(x)=2x^3−24x+25 is increasing or decreasing.
Analyze the first derivative to determine intervals of increase and decrease.
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Show that of all rectangles with a given area, the square has the least perimeter.
The square minimizes perimeter for a given area due to equal side lengths.
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Show that the height of the cylinder of maximum volume that can be inscribed in a sphere of radius R is 2R/√3.
Height = 2R/√3.
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An open tank with square base and vertical sides is to be constructed so as to hold a given quantity of water. Show that the cost of material is least when the depth of the tank is half the width.
Depth = 0.5 * Width minimizes cost.
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The combined resistance R of two resistors R1 and R2 is given by 1/R=1/R1+1/R2, R1,R2>0. If R1+R2=C, where C is a constant, show that the maximum resistance R is obtained by setting R1=R2.
Max resistance occurs at R1=R2.
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Show that among all rectangles inscribed in a given circle, the square has the maximum area.
The square has the maximum area among inscribed rectangles.
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Determine two positive integers whose sum is 15 and the product of the square of one with the other number is maximum.
Integers are 7 and 8.
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A wire of length 28m is to be cut into two pieces. One of the pieces is to be made into a square and the other into a circle. What should be the lengths of the two pieces so that the combined area of the square and the circle is minimum?
Lengths are 14m for square and 14m for circle.
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Show that of all rectangles with given perimeter, the square has the maximum area.
Square maximizes area for fixed perimeter.
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Find the intervals in which the function \( f(x) = 2x^2 - 3x \) is increasing.
Increasing on \( (1.5, \infty) \)
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The radius of a circle is increasing uniformly at the rate of 3 cm/sec. Find the rate at which the area of the circle is increasing when the radius is 15 cm.
Rate of area increase = 90π cm²/sec
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Let \( r, h, V \) be the radius, height and volume of a cone having semi-vertical angle \( heta \) with slant height \( l \), then show that \( V = rac{1}{3} \pi r^2 h \).
Volume \( V = rac{1}{3} \pi r^2 h \)
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Show that the semi-vertical angle of the cone of maximum volume is \( an^{-1}(\sqrt{2}) \).
Semi-vertical angle \( heta = an^{-1}(\sqrt{2}) \)
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Find the interval in which the function \( f(x) = x^2 - 4x + 6 \) is increasing or decreasing in \( R \).
Increasing on \( (2, \infty) \); decreasing on \( (-\infty, 2) \)
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Consider two concentric circles \( C_1 \) and \( C_2 \) with radii \( r_1 \) and \( r_2 \) respectively, given \( r_1 < r_2 \). Given \( r_1 \) increases at the rate of 0.5 cm/s and \( r_2 \) decreases at the rate of 0.7 cm/s. Find the rate of change of the area between \( C_1 \) and \( C_2 \) when \( r_1 = 3 \) cm and \( r_2 = 5 \) cm.
Rate of change of area = -1.2π cm²/s
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Find the intervals in which the function \( f(x) = x^3 - 3x + 1 \) is decreasing and increasing.
Increasing on \( (-\infty, -\sqrt{3}) \cup (\sqrt{3}, \infty) \); decreasing on \( (-\sqrt{3}, \sqrt{3}) \)
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Find the intervals in which the function \( f(x) = x^2 - 4x + 6 \) is strictly increasing and strictly decreasing.
Strictly increasing on \( (2, \infty) \); strictly decreasing on \( (-\infty, 2) \)
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Find the rate of change of area of a circle with respect to its radius \( r \) when \( r = 5 \).
Rate of change = 10π cm²/s
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Find the local maxima or local minima of the function \( f(x) = x^3 - 4x + 1 \) if it exists.
Local minima at \( x = 0 \)
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The radius of a circle is increasing uniformly at the rate of 5 cm/sec. Find the rate at which the area of the circle is increasing when the radius is 8 cm.
Rate of area increase = 40π cm²/sec
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An edge of a cube is increasing at the rate of 4 cm/s. How fast is the volume increasing when the edge is 20 cm?
Volume increasing at 480 cm³/s
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Find the interval in which the function \( f(x) = x^2 - 6x + 5 \) is increasing.
Increasing on \( (3, \infty) \)
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The length \( x \) of a rectangle is increasing at the rate of 4 cm/s and the width \( y \) is decreasing at the rate of 5 cm/s. Find the rates of change of its area when \( x = 10 \) cm and \( y = 5 \) cm.
Rate of change of area = -15 cm²/s
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Show that the function \( f(x) = x^3 + 3x + 5 \) is strictly increasing on \( R \).
f'(x) > 0 for all \( x \in R \)
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Find the interval at which \( f(x) = 10 - 6x - 2x^2 \) is increasing or decreasing.
Increasing on \( (-\infty, -3) \) and decreasing on \( (-3, \infty) \)
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Show that the function \( f(x) = x^3 - 3x^2 + 4x \) is always increasing on \( R \).
f'(x) > 0 for all \( x \in R \)
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Find the minimum value of the function \( f(x) = x^2 + 1 \).
Minimum value is 1 at \( x = 0 \)
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Find the rate of change of area of a circle with respect to its radius \( r \) when \( r = 5 \) cm.
Rate of change = 10π cm²/s
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Show that the function \( f(x) = 2x^3 - 3x^2 + 4x \) is always increasing on \( R \).
f'(x) > 0 for all \( x \in R \)
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Find the intervals in which the function f(x)=x^2−4x+6 is strictly increasing.
The function is increasing where its derivative is positive.
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Find the minimum and maximum value, if any, of the function f(x)=(2x−1)^2+3.
Minimum value is 3 at x=0.5.
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Find two positive numbers whose sum is 15 and sum of whose squares is minimum.
The numbers are 7.5 and 7.5.
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The radius of a cylinder increases at a rate of 1cm/s and its height decreases at a rate of 1cm/s. Find the rate of change of its volume when the radius is 5cm and the height is 15cm.
Use the volume formula V=πr^2h and apply the chain rule.
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Find the intervals in which the function f(x)=x^2−2x+5 is strictly increasing.
The function is increasing for all x.
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A spherical bubble is decreasing in volume at the rate of 2 cm³/sec. Find the rate at which the surface area is diminishing when the radius is 3cm.
Use the relationship between volume and surface area to find the rate.
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Find two numbers whose sum is 24 and whose product is as large as possible.
The numbers are 12 and 12.
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Show that the semi-vertical angles of the cone of maximum volume and of given slant height is tan⁻¹(√2).
Semi-vertical angle = tan⁻¹(√2).
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Show that of all rectangles of given perimeter, the square has the largest area.
Square maximizes area for fixed perimeter.
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Find the least value of 'a' such that the function f(x)=x²+ax+1 is increasing on (1,2).
Least value of a = -2.
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What is the maximum value of the function \( f(x) = x^2 + 4x + 4 \)?
Maximum value is 4 at \( x = -2 \)
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A spherical bubble is decreasing in volume at the rate of 2 c.c/s. Find the rate at which the surface area is diminishing when the radius is 3 cm.
Rate of surface area diminishing = 12π cm²/s.
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Prove that the function f(x)=x³−3x²+3x−100 is increasing on R.
f'(x) > 0 for all x.
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The radius of a circle is increasing at the rate of 3 cm./sec. What rate is the area increasing when the radius is 10 cm?
Rate of area increasing = 60π cm²/s.
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Find the least value of 'a' such that f(x)=x²+ax+1 is increasing on [1,2].
Least value of a = -2.
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Show that f(x)=x³+x²+x+1 does not attain the maximum or minimum value for any real number.
f(x) is unbounded as x → ±∞.
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The radius of a circular plate is increasing at the rate of 0.2 cm/sec. At what rate is the area increasing when the radius of the plate is 2 cm?
Rate of area increasing = 0.8π cm²/s.
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If the radius of a circle is increased from 6 to 6.1 cm, find the approximate increase in its area.
Approximate increase = 1.2π cm².
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Find the intervals in which the function \( f(x) = x^3 - 4x \) is increasing.
(0, 2)
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Which of the following is an increasing function in \( R \)?
f(x) = x^3
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The figure shows the graph of \( f'(x) \). Then the function \( f(x) \) has a local maximum at \( x = 4 \).
has a local maximum at x = 4
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Which of the following function is increasing in its domain?
f(x) = 2x^3 - 3x^2 + 4
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Which of the following function is always increasing on \( R \)?
f(x) = x^4
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Maximum value of f(x)=e^x in [1,2] is
e
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The rate of change of volume of a sphere with respect to its radius when radius is 1 unit.
4π
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The rate of change of area of a circle with respect to radius r, when r = 5 cm.
25π cm²/s
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Which of the following functions has neither local maxima nor local minima?
f(x)=logx
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Which of the following functions is always increasing?
2x+x^3
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