How to Use the Chain Rule to Differentiate :
Here we are going to see how we use chain rule to differentiate.
Question 1 :
Differentiate y = (2x - 5)4 (8x2 - 5)-3
Solution :
To find dy/dx, first we have to use the product rule, in the product rule itself we have to use the chain rule.
u = (2x - 5)4
u' = 4(2x - 5)3 (2) ==> 8 (2x - 5)3
v = (8x2 - 5)-3
v' = -3(8x2 - 5)-4 (16x) ==> -48x(8x2 - 5)-4
d(uv) = uv' + vu'
= (2x - 5)4(-48x(8x2 - 5)-4) + (8x2 - 5)-3(8 (2x - 5)3)
= -48x [(2x - 5)4/(8x2 - 5)4] + 8[(2x - 5)3/(8x2 - 5)3]
= 8((2x - 5)3/(8x2 - 5)4)[-6x(2x - 5) + (8x2 - 5)]
= 8((2x - 5)3/(8x2 - 5)4)[-12x2 + 30x + 8x2 - 5]
= 8((2x - 5)3/(8x2 - 5)4)[-4x2 + 30x - 5]
Question 2 :
Differentiate y = (x2 + 1)∛(x2 + 2)
Solution :
To find dy/dx, first we have to use the product rule, in the product rule itself we have to use the chain rule.
u = (x2 + 1)
u' = 2x + 0 ==> 2x
v = ∛(x2 + 2) = (x2 + 2)1/3
v' = (1/3)(x2 + 2)-2/3(2x)
d(uv) = uv' + vu'
= (x2 + 1)(2x/3)(x2 + 2)-2/3 + (x2 + 2)1/3(2x)
= [2x(x2 + 1)/3(x2 + 2)2/3] + 2x(x2 + 2)1/3
= (2x3 + 2x)+6x((x2 + 2))/(x2 + 2)2/3
= (2x3 + 2x)+6x((x2 + 2))/3(x2 + 2)2/3
= (2x3 + 2x + 6x3 + 12x)/3(x2 + 2)2/3
= (8x3 + 14x)/(x2 + 2)2/3
Question 3 :
Differentiate y = xe^(-x2)
Solution :
To find dy/dx, first we have to use the product rule, in the product rule itself we have to use the chain rule.
u = x
u' = 1
v = e^(-x2)
v' = e^(-x2) (-2x) ==> -2xe^(x2)
d(uv) = uv' + vu'
= x (-2xe^(-x2))+ e^(-x2) (1)
= e^(-x2)[ -2x2 + 1]
= e^(-x2)[1 - 2x2]
Question 4 :
Differentiate y = ∜(t3 + 1)/(t3 - 1)
Solution :
To find dy/dx, we have to use the quotient rule, in the quotient rule itself we have to use the chain rule.
y = ∜(t3 + 1)/(t3 - 1)
y4 = (t3 + 1)/(t3 - 1)
Differentiate with respect to "t"
u = (t3 + 1)
u' = 3t2
v = (t3 - 1)
v' = 3t2
4y3 (dy/dt) = [(t3 - 1) 3t2 - (t3 + 1) (3t2)]/(t3 - 1)2
dy/dt = [(t3 - 1) 3t2 - (t3 + 1) (3t2)]/4y3(t3 - 1)2
dy/dt = (3t5 - 3t2 - 3t5 - 3t2)/4((t3+1)/(t3-1))3/4(t3-1)2
dy/dt = (- 3t2 )/(2((t3+1)3/4(t3-1)2/(t3-1))3/4)
dy/dt = (- 3t2 )/(2((t3+1)3/4(t3-1))2-3/4)
dy/dt = (- 3t2 )/(2((t3+1)3/4(t3-1))5/4)
After having gone through the stuff given above, we hope that the students would have understood, "How to Use the Chain Rule to Differentiate"
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