F(x)=7-5x+7x^2. Find f(-9a)

Question

I don't have a clue what I'm doing  what that even is so please help.                                  

Answer 1

Hello, Idk,

These equations are written with an f(x), instead of a "y."  They are written in what is called function notation. You might be more familiar with the other way of writing them, such as:    y= 7-5x +7x²and f(-9a) means that they are telling you what the value of "x" is which is x=-9a.  They want you to find "y."  This is how you can set up the problem using substitution for the value of "x":

 

y= 7- 5(-9a) + 7 (-9a)²                                                   Note:          7(-9a)²    =  7*(-9a)(-9a)=   7*81a²

 

You need to simplify by collecting like terms.   Now all you have to do is finish your problem.  Susan C.

Answer 2

f(-9a ) = 7 - 5(-9a) + 7(-9a)²

f(-9a) = 7 + 45a + 567a²