Math Is Fun Forum

kgh

Member

Registered: 2009-02-08

Posts: 11

determine the slope of the tangent when x coordinate is a

Determine the slope of the tangent to the graph of y=2x^2+3x at the general point whose x coordinate is a.

I have to use limits to solve this problem and I'm having trouble with the algebra involved. This is where I'm stuck:

lim     2x^2+3x-(2a^2-3a)
x->a            x-a

Do I factor out the x and then factor out the a? Or do I factor out the 2 from the 2x^2 and the 2a^2 and then the 3 from the 3x^2 and 3a^2? I know the answer is 4x-3, I'm just having trouble getting there. Thanks!

coffeeking

Member

Registered: 2007-11-18

Posts: 44

Re: determine the slope of the tangent when x coordinate is a

Ok, starting from

Therefore