# The graph of #y=ax^2+bx# has an extremum at #(1,-2)#. Find the values of a and b?

##### 2 Answers

May 23, 2018

#### Explanation:

Given:

From the given can substitute 1 for x and 2 for y and write the following equation:

We can write the second equation using that the first derivative is 0 when

Subtract equation [1] from equation [2]:

Find the value of b by substituting

May 23, 2018

#### Explanation:

#1# #in# #RR# #f# is differentiable at#x_0=1# #f# has an extremum at#x_0=1#

According to Fermat's Theorem

but

So

and

so