The slope at each point (x, y) and the graph of y = f (x) is given by x[x^(2)-1]^(1/3) and the graph passes through the point (3,1). Find the equation for f?
step by step please, I am lost.
step by step please, I am lost.
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This is a separable differential equation...
slope = dy/dx = x(x^2 - 1)^(1/3)
dy = x(x^2 - 1)^(1/3) dx
we need to integrate both sides....
let u=x^2 -1
then du/2 = x dx
plug that into the right side...
integrate 0.5u^(1/3) du
(3/8) u^(4/3) + C
plug "u" back in...
y = (3/8) (x^2-1)^(4/3) + C
To find "C" plug in the point...
1 = (3/8)(3^2-1)^(4/3) + C
C = -5.
So your answer is....
y = (3/8) (x^2-1)^(4/3) -5
slope = dy/dx = x(x^2 - 1)^(1/3)
dy = x(x^2 - 1)^(1/3) dx
we need to integrate both sides....
let u=x^2 -1
then du/2 = x dx
plug that into the right side...
integrate 0.5u^(1/3) du
(3/8) u^(4/3) + C
plug "u" back in...
y = (3/8) (x^2-1)^(4/3) + C
To find "C" plug in the point...
1 = (3/8)(3^2-1)^(4/3) + C
C = -5.
So your answer is....
y = (3/8) (x^2-1)^(4/3) -5
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This is an integration problem. To do it, you have to look at some function that will differentiate into y' = x[x^2-1]^1/3
Let u = x^2 - 1
du = 2x*dx
dx = du/2x
So integrate u^1/3 du/2
This gives u^(4/3)/[2*4/3] = (3/8)*u^4/3 + C
Which when you substitute for u gives y = (3/8) (x^2 -1)^(4/3) + C
Now we can solve for C
y = 1
x = 3
1 = (3/8) (8)^(4/3) + C
1 = (3/8) * 16 + C
1 = 6 + C
C = - 5
So the final answer is
y = (3/8) (x^2 - 1) ^ (4/3) - 5
Let u = x^2 - 1
du = 2x*dx
dx = du/2x
So integrate u^1/3 du/2
This gives u^(4/3)/[2*4/3] = (3/8)*u^4/3 + C
Which when you substitute for u gives y = (3/8) (x^2 -1)^(4/3) + C
Now we can solve for C
y = 1
x = 3
1 = (3/8) (8)^(4/3) + C
1 = (3/8) * 16 + C
1 = 6 + C
C = - 5
So the final answer is
y = (3/8) (x^2 - 1) ^ (4/3) - 5
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The slope at x is f '(x)
therefore
f(x) = ∫x[x^(2)-1]^(1/3) dx = (*)
set
x^2 - 1 = u
2x dx = du
x dx = du/2
(*) = (1/2)∫u^(1/3) du = (1/2) (1/(1/3+1)) u^(1/(1/3+1)) + C
= (3/8)u^(3/4) + C = (3/8)(x^2 - 1)^(4/3) + C
f(3) = 1
f(3) = (3/8)(3^2 - 1)^(4/3) + C = 1
(3/8)8^(4/3) + C = 1
C= 1 - (3/8)8^(4/3) = 1 - (3/8)· 8· (8^1/3) = 1 - 3· 2 = -5
f(x) = (3/8)(x^2 - 1)^(4/3) - 5
therefore
f(x) = ∫x[x^(2)-1]^(1/3) dx = (*)
set
x^2 - 1 = u
2x dx = du
x dx = du/2
(*) = (1/2)∫u^(1/3) du = (1/2) (1/(1/3+1)) u^(1/(1/3+1)) + C
= (3/8)u^(3/4) + C = (3/8)(x^2 - 1)^(4/3) + C
f(3) = 1
f(3) = (3/8)(3^2 - 1)^(4/3) + C = 1
(3/8)8^(4/3) + C = 1
C= 1 - (3/8)8^(4/3) = 1 - (3/8)· 8· (8^1/3) = 1 - 3· 2 = -5
f(x) = (3/8)(x^2 - 1)^(4/3) - 5
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f(x) = (3/8)[x^(2)-1]^(4/3) + C , plug (3,1) to find C