## anonymous one year ago If ƒ(x ) = x 2 + 1 and g(x ) = 3x + 1, find 2 · ƒ(4).

1. anonymous

@Nnesha

2. SolomonZelman

$$\large\color{purple}{ \displaystyle f(x)=x^2+1 }$$ $$\large\color{brown}{ \displaystyle g(x)=3x+1 }$$ To find $$2\cdot f(2)$$ you don't need the $$g(x)$$. Just, plug in 2 instead of x into the $$f(x)$$, and then multiply the result times two.

3. Nnesha

4*

4. SolomonZelman

Ok, if I wanted to find: $$4\cdot f(3)$$ then this is what I would do: $$\large\color{black}{ \displaystyle f(x)=x^2+1 }$$ Plug in 3 instead of x: $$\large\color{black}{ \displaystyle f(\color{red}{3})=\color{red}{3}^2+1 }$$ I know that $$3^2=9$$, so I can write that: $$\large\color{black}{ \displaystyle f(3)=9+1 }$$ And then, obviously, 9+1=10, so this is what I get for $$f(3)$$. $$\large\color{black}{ \displaystyle f(3)=10 }$$ Now, I have to multiply: I am asked to find $$4 \cdot f(3)$$, and since I know that $$f(3)=10$$, I can just go ahead and apply that (substitute 10 for f(3) ): $$\large\color{black}{ \displaystyle 4\cdot f(3)=4 \cdot 10 = 40 }$$

5. SolomonZelman

(hope this is a helpful example)

6. anonymous

i got an answer that wasnt one of the options

7. Nnesha

what did you get ?

8. anonymous

5.3

9. SolomonZelman

That is not possible

10. SolomonZelman

$$\large\color{black}{ \displaystyle f(x)=x^2+1 }$$ $$\large\color{black}{ \displaystyle f(4)=\bf ? }$$

11. anonymous

i said i did it wrong then i redid it and got it right