Question

Solve | x + 6| - 7 = 8

Answer 1

Answer:

x = 9,-21

Step-by-step explanation:

Given:

$\displaystyle \large{|x+6|-7=8}$

Transport -7 to add 8:

$\displaystyle \large{|x+6|=8+7}\\\displaystyle \large{|x+6|=15}$

Cancel absolute sign and add plus-minus to 15:

$\displaystyle \large{x+6=\pm 15}$

Transport 6 to subtract ±15:

$\displaystyle \large{x=\pm 15-6}$

Consider:

$\displaystyle \large{x= 15-6}$ or $\displaystyle \large{x = -15-6}$

$\displaystyle \large{x=9}$ or $\displaystyle \large{x=-21}$

Solution:

$\displaystyle \large{x = 9}$ or $\displaystyle \large{x=-21}$

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Second Method

Given:

$\displaystyle \large{|x+6|-7=8}$

Transport -7 to add 8:

$\displaystyle \large{|x+6|=8+7}\\\displaystyle \large{|x+6|=15}$

Absolute Function Property:

$\displaystyle \large{|x-a| = \begin{cases} x-a \ \ (x \geq a) \\ -x+a \ \ (x < a) \end{cases}}$

Consider both intervals:

When x ≥ a then:

$\displaystyle \large{|x+6|=15}\\\displaystyle \large{x+6=15}$

Transport 6 to subtract 15:

$\displaystyle \large{x=15-6}\\\displaystyle \large{x=9}$

When x < a then:

$\displaystyle \large{|x+6|=15}\\\displaystyle \large{-(x+6)=15}\\\displaystyle \large{-x-6=15}$

Transport -6 to add 15:

$\displaystyle \large{-x=15+6}\\\displaystyle \large{-x=21}$

Transport negative sign to 21:

$\displaystyle \large{x=-21}$

Solution:

$\displaystyle \large{x=9}$ or $\displaystyle \large{x=-21}$

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