# Math Help - Limits and functions

1. ## Limits and functions

Okay I have 2 questions.

If $f(x)=2x^2+3x+5$

Find
$\displaystyle \Large \lim _{h\to 0}\frac{f(h)-f(0)}{h}$

and

If
$

f(x)=-(25/2x+3)

$

Find

$\displaystyle \Large \lim _{h\to 0}\frac{f(1+h)-f(1)}{h}$

A 2
B 3
C +infinity
D 1
E Does Not Exist
F 0
G 4
H None of the above

I've tried and asked my friends and no one knows how to start this.

2. Originally Posted by tofuwrice
Okay I have 2 questions.

If $f(x)=2x^2+3x+5$

Find
$\displaystyle \Large \lim _{h\to 0}\frac{f(h)-f(0)}{h}$

[snip]
Start by getting an expression for f(h). Then get f(0). Then get f(h) - f(0) and simplify. Then divide the result by h. Then take the limit. Alternatively, recognise the value of the limit as f'(0).

Originally Posted by tofuwrice
[snip]
If

Find

$\displaystyle \Large \lim _{h\to 0}\frac{f(1+h)-f(1)}{h}$

A 2
B 3
C +infinity
D 1
E Does Not Exist
F 0
G 4
H None of the above

I've tried and asked my friends and no one knows how to start this.
See the approach I advised for the first question. Alternatively, recognise the value of the limit as f'(1).