Answer
Evaluate $f(x) = x^{2}+2x$:
$f(0)=0$
$f(3) = 15$
$f(-3) = 3$
$f(a) = a^{2}+2a$
$f(-x) = x^{2}-2x$
$f(\frac{1}{a}) =\frac{1}{a^{2}} +\frac{2}{a}$
Work Step by Step
x = 0
$f(0) = 0^{2}+2(0)$ ... square 0 and multiply $2\times0$
$= 0 +0$ ... add
$= 0$
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x = 3
$f(3) = 3^{2}+2(3)$ ... square 3 and multiply $2\times3$
$= 9 +6$ ... add
$= 15$
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x = -3
$f(-3) = (-3)^{2}+2(-3)$ ... square -3 and multiply $2\times(-3)$
$= 9 + (-6) $ ... add
$= 3$
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x = a
$f(a) = a^{2}+2(a)$
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x = -x
$f(-x) = (-x)^{2}+2(-x)$ ... square (-x) and multiply $2\times(-x)$
$= x^{2} + (-2x)$ ... simplify
$= x^{2} - 2x$
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x = $\frac{1}{a}$
$f(\frac{1}{a}) = (\frac{1}{a})^{2}+2(\frac{1}{a})$ ... square $\frac{1}{a}$ and multiply $2\times\frac{1}{a}$
$= \frac{1}{a^{2}} +\frac{2}{a}$
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