Question

tìm xϵz :

a)15 - ( x - 7 ) = -21

b) 3x + 17 = 2 

c) 45 - ( x - 9 ) = -35

d)(-5) + x = 15

e) 2x - (-17) = 15 

g) | x - 2 | = 3 

 

Answer 1

a.

\(15-\left(x-7\right)=-21\)

\(x-7=15-\left(-21\right)\)

\(x-7=36\)

\(x=36+7\)

\(x=43\)

b.

\(3x+17=2\)

\(3x=2-17\)

\(3x=-15\)

\(x=-15\div3\)

\(x=-5\)

c.

\(45-\left(x-9\right)=-35\)

\(x-9=45-\left(-35\right)\)

\(x-9=80\)

\(x=80+9\)

\(x=89\)

d.

\(\left(-5\right)+x=15\)

\(x=15-\left(-5\right)\)

\(x=20\)

e.

\(2x-\left(-17\right)=15\)

\(2x=15+\left(-17\right)\)

\(2x=-2\)

\(x=-2\div2\)

\(x=-1\)

g.

\(\left|x-2\right|=3\)

\(x-2=\pm3\)

\(x-2=3\)

               \(x=3-2\)

               \(x=1\)

\(x-2=-3\)

                \(x=-3+2\)

                \(x=-1\)

Vậy x = 1 hoặc x = - 1.

Chúc bạn học tốt

Answer 2

a)

15-(x-7)=-21

x-7=15-(-21)

x-7=36

x=36+7

x=43

b)

3x+17=2

3x=17-2

3x=15

x=15:3

x=5

c)

45-(x-9)=-35

x-9=45-(-35)

x-9=80

x=80+9

x=89

d)

(-5)+x=15

x=15-(-5)

x=20

e)

2x-(-17)=15

2x=15+(-17)

2x=-2

x=-2:2

x=-1

g)

TH1

|x-2|=3

x-2=3

x=3+2

x=5

TH2

|x-2|=3

x-2=-3

x=-3+2

x=-1