Question

Bài 1:tìm x thuộc số nguyên 
a, 45-15=-75-x

b,(6+x).(3-x)=0

c,x² - 8 x = 0

d,-3.|x-7| =-21

Answer 1

a) 45 -15 = -75 -x

45 -15 + 75 = -x

105 = -x

=> x= -105

Vậy...

Answer 2

a, 45-15=-75-x

=> 30 = -75 - x

=> x = -75 - 30

=> x = -105

Answer 3

b) (6+x).(3-x)=0

=> 6+x = 0 hoặc 3-x= 0

Nếu 6+x = 0 thì x = 0-6 => x = -6

Nếu 3 -x = 0 => x = 3-0 => x =3

Vậy...

Answer 4

d,-3.|x-7| =-21

| x -7 | = -21 : ( -3)

| x-7| = 7

TH1: x - 7 =  7

x= 7+7 => x= 14

TH2: x -7 = -7

x= ( -7) +7

x= 0

Vậy...

Answer 5

\(a.45-15=-75-x\)

\(x=-75-45+15\)

\(x=-105\)

Vậy \(x\in\left\{-105\right\}\)

\(b.\left(6+x\right)\left(3-x\right)=0\)

\(\Rightarrow TH1:6+x=0\)

            \(x=0-6\)

            \(x=-6\)

    \(TH2:3-x=0\)

                  \(x=3-0\)

                  \(x=3\)

Vậy \(x\in\left\{3;-6\right\}\)

\(c.x^2-8x=0\)

  \(x\left(x-8\right)=0\)

  \(\Rightarrow TH1:x=0\)

      \(TH2:x-8=0\)

              \(x=0+8\)

              \(x=8\)

Vậy \(x\in\left\{8;0\right\}\)

\(d.-3.|x-7|=-21\)

          \(|x-7|=-21:-3\)

          \(|x-7|=7\)

\(\Rightarrow TH1:x-7=7\)

            \(x=7+7\)

            \(x=14\)

    \(TH2:x-7=-7\)

            \(x=-7+7\)

            \(x=0\)

Vậy \(x\in\left\{0;14\right\}\)

Answer 6

\(a,45-15=-75-x\\ =>30=-75-x\\ =>x=-75-30\\ =>x=-105\)