Given that f(x)=2x -5, how do you find the value of x that makes f(x)=15?

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Given that f(x)=2x -5, how do you find the value of x that makes f(x)=15?

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Answer 1 · 2016-12-08T01:28:15

$x = 10$ $x=10$

Explanation:

$f (x) = 2 x - 5$ $\color(red)(f(x)=2x-5)$ and $f (x) = 15$ $\color(red)(f(x))=15$
therefore...
$2 x - 5 = f (x) = 15 \Rightarrow 2 x - 5 = 15$ $2x-5=f(x)=15\rArr2x-5=15$
so you now have an equation to solve:
$2 x - 5 = 15$ $2x-5=15$

add 5 to both sides... $2x\cancel(-5+5)=15+5$
simplify $2x=20$
divide both sides by 20... $(\cancel(2)x)/\cancel(2)=20/2$
simplify $x=20/2=10$

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Given that f(x)=2x -5, how do you find the value of x that makes f(x)=15?

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