Solve | x + 6| - 7 = 8

A: x= -9 and x = -21

B: x = 9 and x = -9

C: x = -9 and x = 21

D: x = 9 and x = -21


Sagot :

Answer:

x = 9,-21

Step-by-step explanation:

Given:

[tex]\displaystyle \large{|x+6|-7=8}[/tex]

Transport -7 to add 8:

[tex]\displaystyle \large{|x+6|=8+7}\\\displaystyle \large{|x+6|=15}[/tex]

Cancel absolute sign and add plus-minus to 15:

[tex]\displaystyle \large{x+6=\pm 15}[/tex]

Transport 6 to subtract ±15:

[tex]\displaystyle \large{x=\pm 15-6}[/tex]

Consider:

[tex]\displaystyle \large{x= 15-6}[/tex] or [tex]\displaystyle \large{x = -15-6}[/tex]

[tex]\displaystyle \large{x=9}[/tex] or [tex]\displaystyle \large{x=-21}[/tex]

Solution:

[tex]\displaystyle \large{x = 9}[/tex] or [tex]\displaystyle \large{x=-21}[/tex]

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Second Method

Given:

[tex]\displaystyle \large{|x+6|-7=8}[/tex]

Transport -7 to add 8:

[tex]\displaystyle \large{|x+6|=8+7}\\\displaystyle \large{|x+6|=15}[/tex]

Absolute Function Property:

[tex]\displaystyle \large{|x-a| = \begin{cases} x-a \ \ (x \geq a) \\ -x+a \ \ (x < a) \end{cases}}[/tex]

Consider both intervals:

When x ≥ a then:

[tex]\displaystyle \large{|x+6|=15}\\\displaystyle \large{x+6=15}[/tex]

Transport 6 to subtract 15:

[tex]\displaystyle \large{x=15-6}\\\displaystyle \large{x=9}[/tex]

When x < a then:

[tex]\displaystyle \large{|x+6|=15}\\\displaystyle \large{-(x+6)=15}\\\displaystyle \large{-x-6=15}[/tex]

Transport -6 to add 15:

[tex]\displaystyle \large{-x=15+6}\\\displaystyle \large{-x=21}[/tex]

Transport negative sign to 21:

[tex]\displaystyle \large{x=-21}[/tex]

Solution:

[tex]\displaystyle \large{x=9}[/tex] or [tex]\displaystyle \large{x=-21}[/tex]

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