# Derivatives

• October 29th 2007, 07:28 AM
Fnus
Derivatives
I'm at such a loss.
In exercise 4 I don't even know where to being, and in exercise 9 the x=a confuses me.
• October 29th 2007, 09:48 AM
Sean12345
4a) We have $2x+y=6; x=1 \implies y=4$
Also we know the gradient; $m=-2$
Differentiate $y=x^2+ax+b$

$\implies \frac {dy}{dx} = 2x+a$

$\implies 2x+a=-2$

$x=1; 2(-1)+a=-2$

$\implies a=0$

$\implies y=x^2+b$

$x=1, y=-4; -4=1^2+b$

$\implies b=-5$

b is similar so ill let you try.