Question

Need help guys plss solve this and show your solutions :
Problem : Find the derivatives of the function .
y=(2x-7)(x+3)

Answer 1

multiply it out
2x^2-x-21

take derivative
2*2x-1
= 4x-1

Answer 2

^ that or you can use the product rule which is y' = f'g+ fg', if they are tell you to do it with that specific method

Answer 3

the answer is wrong . need more help plss. Our topic is definition of derivatives

Answer 4

So you need to use the limit definition for this problem?
\[\huge f'(x)=\lim_{h \rightarrow 0} \frac{f(x+h)-f(x)}{h}\]

Answer 5

yes

Answer 6

Oh boy :\

Answer 7

Hmm well I still think multiplying them out first is going to be the easier way, but not by much hehe.

Answer 8

Write y as a function of x, it might make this a little easier on the notation.
\[\huge f(x)=2x^2-x-21\]\[\huge f(x+h)=2(x+h)^2-(x+h)-21\]

Answer 9

And then plugging it in, you get something like this... and need to do a bunch of simplification :3 oh boy!\[\large \lim_{h \rightarrow 0} \frac{2(x+h)^2-(x+h)-21-(2x^2-x-21)}{h}\]

Answer 10

answer : 4x ??

Answer 11

Hmm there shoulda been a 1 in there somewhere :D
I think you'll get 4x-1 somehow.