SOLUTION: let f(x) = 3x^2 + 2x -1 and g(x) = 5x + 7 find (fog)(-2) HELP!!!!!

Algebra ->  Exponential-and-logarithmic-functions -> SOLUTION: let f(x) = 3x^2 + 2x -1 and g(x) = 5x + 7 find (fog)(-2) HELP!!!!!      Log On


   

Question 1158340: let f(x) = 3x^2 + 2x -1 and g(x) = 5x + 7 find (fog)(-2)
HELP!!!!!
Found 3 solutions by josgarithmetic, ikleyn, MathTherapy:
Answer by josgarithmetic(39618) About Me  (Show Source):
You can put this solution on YOUR website!
(fog)(-2)

Meaning is f%28g%28-2%29%29

Answer by ikleyn(52790) About Me  (Show Source):
You can put this solution on YOUR website!
.

The easiest way is to calculate g(-2) first


    g(-2) = 5*(-2) + 7 = -10 + 7 = -3.


and then substitute this value  g(-2) = -3 into the formula for f(x).


So,  (fog) (-2) = f(-3) = 3*(-3)^2 + 2*(-3) - 1  = 27 - 6 - 1 = 20  is your answer.

Solved.

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The meaning of this operation,  (fog),  which is called  "the composition of functions g and f",  is that
the output of  "g"  becomes the input for  "f".


Answer by MathTherapy(10552) About Me  (Show Source):
You can put this solution on YOUR website!
let f(x) = 3x^2 + 2x -1 and g(x) = 5x + 7 find (fog)(-2)
HELP!!!!!
Follow the instructions by TUTOR @IKLEYN.

g(- 2) = 5(- 2) + 7 = - 10 + 7 = - 3

So, you'll get .