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aleksandr82 [10.1K]
4 years ago
12

Suppose y varies with x, and y=30 when x=3. What direct variation equation relates x and y?

Mathematics
1 answer:
In-s [12.5K]4 years ago
6 0
Direct variation:  y = kx.

Here, 30 = k(3), so k = 10.

Thus, the direct variation equation relating x and y is   y = 10x.
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F(x) is a piecewise function defined as:
f(x) = (3/2)x when 0 <= x <= 2
or
f(x) = -(3/2)x+6 when 2 < x <= 4

g(x) is defined as: 
g(x) = -(1/4)x+1 when 0 <= x <= 4

Based on the graph or through the equations we can say:
f(1) = (3/2)*1 = 1.5
g(1) = -(1/4)*1+1 = 0.75
f(3) = (3/2)*3 = 4.5
g(3) = -(1/4)*3+1 = 0.25

And the derivative values are:
f ' (1) = 3/2 = 1.5
f ' (3) = -3/2 = -1.5
g ' (1) = -1/4 = -0.25
g ' (3) = -1/4 = -0.25
which are the slopes of each line

So...
h(x) = f(x)*g(x)
h ' (x) = f ' (x)*g(x) + f(x)*g ' (x) ... product rule
h ' (1) = f ' (1)*g(1) + f(1)*g ' (1)
h ' (1) = 1.5*0.75 + 1.5*(-0.25)
h ' (1) = 0.75

and,
h(x) = f(x)*g(x)
h ' (x) = f ' (x)*g(x) + f(x)*g ' (x)
h ' (3) = f ' (3)*g(3) + f(3)*g ' (3)
h ' (3) = -1.5*0.25 + 4.5*(-0.25)
h ' (3) = -1.5
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Use the law of cosines to find the value of cos theta. round your answer to two decimal places.
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4 years ago
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