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Evaluate the function F(X)

Evaluate the function f(X)=5x+2




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Kit Chun L. | Columbia Grad for Math and SAT tutoringColumbia Grad for Math and SAT tutoring
4.9 4.9 (153 lesson ratings) (153)

Hi Betty,
In this problem, you are given a function f(x) = 5x+2 and you are asked to evaluate f(-9), f(x+1), f(-x). Recall that f(x) = y. When we evaluate functions, we substitute the given x-value to find the corresponding y-value of the function.
That means f(-9) would give the y-value of the function f(x) when x=-9.

f(-9) = 5(-9)+2 = -45+2 = -43

f(x+1) gives the y-value or in this case, an algebraic expression, of f(x) when the domain is x+1.
f(x+1) = 5(x+1)+2 = 5x+5+2 = 5x+7

Similarly, to find f(-x), we replace the x in the function with -x.
f(-x) = 5(-x)+2 = -5x+2