i'm Hoping This Is All I Need.

Find x if f(x) = 2x + 7 and f(x) = -1

OK.......just set  2x + 7  = -1

Subtract 7 from both sides   

2x  = -8        divide by 2 on both sides

x = -4

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Find f(-7) if f(x) = 2x + 8

Just put -7 into f(x) and evaluate....so we have   ...  2(-7) + 8  =  -14 + 8 = -6

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f(-1)   means that we want to stick -1 into x - 5...so we have  -1 - 5 = -6

The rest are done similarly......

Find x if f(x) = 2x + 7 and f(x) = -1.

$$\\ f(x) = 2x+7 \qquad | \qquad f(x) = \textcolor[rgb]{1,0,0}{-1} \\\\
\textcolor[rgb]{1,0,0}{-1} = 2x+7\\\\
2x = -8\\\\
x=-4$$

Find f(-7) if f(x) = 2x + 8.

$$\\ f(x) = 2x+8 \qquad | \qquad x = \textcolor[rgb]{1,0,0}{-7} \\\\
f(\textcolor[rgb]{1,0,0}{-7}) = 2\cdot (\textcolor[rgb]{1,0,0}{-7}) + 8\\\\
f(\textcolor[rgb]{1,0,0}{-7}) = -14+ 8\\\\
f(\textcolor[rgb]{1,0,0}{-7}) = -6$$

If f(x) = x - 5, then match each of the following.

f(-1) = -1 - 5 = -6

f(0) = 0 - 5 = -5

f(1) = 1 - 5 = -4

f(2) = 2 - 5 = -3

f(5) = 5 - 5 = 0

f(8) = 8 - 5 = 3