Question

for f(x)=3x^2+7x+6, find all values of a for which f(a)=4. a=?? (use commas to seperate answers as needed)

Answer 1

Ok, sub a in for x and set the function equal to 4. Solve for a from there.

Answer 2

ok u lost me lol

Answer 3

Ok, you're starting with f(x), but then it asks about f(a), that means x=a, so change that first, because that's what it's asking for.

Answer 4

so it will be f(a)=3a^2+7(a)+6=4 ?

Answer 5

f(a)=4, so after you do that substitution, set the whole function of a = 4, then start solving.

Answer 6

Yes, exactly. See what to do next?

Answer 7

3(4)^2+7(4)+6=4 right?

Answer 8

No, you don't know if a is 4 yet. You know f(a)=4, which means whatever you find for a, when you put that value in it'll make the whole thing equal to 4.

Answer 9

ok so what is my next step

Answer 10

You got your equation, 3a^2+7(a)+6=4
Quadratic equations like this one are easiest to solve when set equal to zero, so if you subtract 4 from each side, the right side goes to zero.

Answer 11

ok

Answer 12

then?

Answer 13

It's factorable . . .

Answer 14

so i factor 3a^2+7a+6=4 ?

Answer 15

But then the quadratic formula always works, so you could use that too.

Answer 16

Subtract 4 from each side and then factor. Get it equal to zero first.

Answer 17

ok i got it..

Answer 18

I knew you would. :-)