Question

[agelina jolie]

tìm xez , biết 

a) |x - 3 | - 7 = 13

b) 72 - 3 . | x + 1 | = 9

c) 17 - ( 43 - |x| ) = 45 

d) 3 | x - 1 | - 5 = 7 

e) -12 ( x - 5 ) + 7 (3 - x ) = 5

Answer 1

[Hồng Trinh]

a. \(\left|x-3\right|-7=13\Leftrightarrow\left|x-3\right|=20\)

TH1: \(x-3=20\Leftrightarrow x=23\)

TH2: \(x-3=-20\Leftrightarrow x=-17\)

b. \(72-3.\left|x+1\right|=9\Leftrightarrow\left|x+1\right|=21\)

TH1: \(x+1=21\Leftrightarrow x=20\)

TH2: \(x+1=-21\Leftrightarrow x=-22\)

c. \(17-\left(43-\left|x\right|\right)=45\Leftrightarrow\left|x\right|=71\)

TH1: \(x=71\)

TH2: \(x=-71\)

d. \(3\left|x-1\right|-5=7\Leftrightarrow\left|x-1\right|=4\)

TH1: \(x-1=4\Leftrightarrow x=5\)

TH2: \(x-1=-4\Leftrightarrow x=-3\)

e. \(-12\left(x-5\right)+7\left(3-x\right)=5\Leftrightarrow-12x+60+21-7x=5\Leftrightarrow-19x=-76\Leftrightarrow x=4\)

Answer 2

[Phương An]

a.

\(\left|x-3\right|-7=13\)

\(\left|x-3\right|=13+7\)

\(\left|x-3\right|=20\)

\(x-3=\pm20\)

• \(x-3=20\)

               \(x=20+3\)

               \(x=23\)

• \(x-3=-20\)

               \(x=-20+3\)

               \(x=-17\)

Vậy x = 23 hoặc x = - 17.

b.

\(72-3\times\left|x+1\right|=9\)

\(3\times\left|x+1\right|=72-9\)

\(3\times\left|x+1\right|=63\)

\(\left|x+1\right|=63\div3\)

\(\left|x+1\right|=21\)

\(x+1=\pm21\)

• \(x+1=21\)

               \(x=21-1\)

               \(x=20\)

• \(x+1=-21\)

               \(x=-21-1\)

               \(x=-22\)

Vậy x = 20 hoặc x = - 22.

c.

\(17-\left(43-\left|x\right|\right)=45\)

\(43-\left|x\right|=17-45\)

\(43-\left|x\right|=-28\)

\(\left|x\right|=43-\left(-28\right)\)

\(\left|x\right|=71\)

\(x=\pm71\)

Vậy x = 71 hoặc x = - 71.

d.

\(3\times\left|x-1\right|-5=7\)

\(3\times\left|x-1\right|=7+5\)

\(3\times\left|x-1\right|=12\)

\(\left|x-1\right|=12\div3\)

\(\left|x-1\right|=4\)

\(x-1=\pm4\)

• \(x-1=4\)

               \(x=4+1\)

               \(x=5\)

• \(x-1=-4\)

               \(x=-4+1\)

               \(x=-3\)

Vậy x = 5 hoặc x = - 3.

e.

\(-12\times\left(x-5\right)+7\times\left(3-x\right)=5\)

\(-12\times x+\left(-12\right)\times\left(-5\right)+7\times3-7\times x=5\)

\(-12\times x+60+21-7\times x=5\)

\(-19\times x+81=5\)

\(-19\times x=5-81\)

\(-19\times x=-76\)

\(x=\frac{-76}{-19}\)

\(x=4\)

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