# Thread: differention using quotient rule

1. ## differention using quotient rule

y = (2x^2 + bx +c) / (x^2 + -5x+4)

1. dy/dx = (4x +b)(x^2 + - 5x + 4) -(2x - 5)(2x^2 + bx + c) (THIS IS INCORRECT)

2. dy/dx = (4xb)(x^2 + - 5x + 4) -(2x - 5)(2x^2 + bx + c) ( this is correct)

2. Hello,

Originally Posted by Goodguy

y = (2x^2 + bx +c) / (x^2 + -5x+4)

1. dy/dx = (4x +b)(x^2 + - 5x + 4) -(2x - 5)(2x^2 + bx + c) (THIS IS INCORRECT)

2. dy/dx = (4xb)(x^2 + - 5x + 4) -(2x - 5)(2x^2 + bx + c) ( this is correct)
The quotient rule says :

$\displaystyle \left(\frac uv\right)'=\frac{u'v-uv'}{\color{red}\bf{v^2}}$

3. Thanks for reply. Yeah I knew the quotient rule. But I just wanted to calculate stationary points so that dy/dx = 0 . so denominator v^2 does not matter. Its the numerator which I am concerned about. I should have pointed this out earlier. Can you tell me numerator in 1. is INCORRECT

y = (2x^2 + bx +c) / (x^2 + -5x+4)

1. dy/dx = (4x +b)(x^2 + - 5x + 4) -(2x - 5)(2x^2 + bx + c) (THIS IS INCORRECT)

2. dy/dx = (4xb)(x^2 + - 5x + 4) -(2x - 5)(2x^2 + bx + c) ( this is correct)