Question

Use only the digits 0 - 9 and the decimal and the negative sign, if needed, to fill in the blank.

If f(x) = 2x + 9, then f(-1) = _____.
It's a fill in the blank, and it's urgent so thanks.

Answer 1

7

Explanation:

f(x) = 2x + 9

For f(-1), replace x by -1

f(-1) = 2(-1) + 9

= -2 + 9

= 7

Answer 2

see below

Explanation:

f(x) = 2x + 9,

Let x = -1

f(-1) = 2(-1) +9

= -2 +9

= 7