f(x) = -15x - 10, g(x) = 12x + 10? find f(f(7))...yes its confusing....teach me how to do such problems?

Question

im starting high school in a week or so and i was told tht i would encounter such problems throughout the year in math class....i thought i would get a head start...i would appreciate it if someone helped

Answer 1

The answer is pretty easy. first of all forget about g(x) since your not doing anything with this.

f(7) means x=7 in this problem so that you replace x with 7 to calculate f(7)

f(7) = -15 * 7 - 10= -115

so f(f(7)) = f(-115) since f(7) = -115

= -15*(-115)-10 = 1715

Just remember that x means a variable or any number. Once you have a given like x=7, substitute where appropriate and do the calculations (remember multiplying two negatives gives a positive, negative and postive give a negative, and two positives a positive.

So as a second example if someone now said I want g(f(f(7))) then they are saying x=1715

so g(1715) = 12*1715+10 = 17160

good luck!

Answer 2

You are talking about functions.
To find f(f(7)) you have to first find f(7).

Take the f(x) function and replace x with 7.
After you substitute for x simplify the expression.
-15(7) -10 = -105-10 = -115. f(7) = -115.

To find f(f(7)) substitute the value that you found for f(7) for x.
-15(-115)-10 = 1725-10 = 1715

So f(f(7)) = 1715.

Good luck with school this year.

Answer 3

Since f(x)=7, then wherevever you see f(x), x, or g(x) place a 7 there. So, for example. f(7) is also known as y=7. Therefore, f(7)= -15(7)-10. -15 times 7 equals -105. -105 minus 10 equals -115. Try the next one, it's very simple! I hope this helped. Good luck in high school.

Answer 4

it means that y (shown by f(x)) is -15x-10. all you have to do is substitute f(x) with 7. solve for x and you are done

Answer 5

i did that in algebra 1 last year and i hated it and i dont even remember how to do it! im in 9th grade now! sorry i cant help!