Câu `1`

`a)(-13).7`

`=-91`

`b)8.(-9)`

`=-72`

`c)245.(-2)`

`=-490`

`d)(-61).(-5)`

`=305`

`e)(-6).|-28|`

`=(-6).28`

`=-168`

`f)(-11).(-91)`

`=1001`

`g)(-20).0`

`=0`

`h)9.17`

`=153`

Câu `2`

`a)x.(x-9)=0`

`TH1:x=0`

`TH2:x-9=0->x=9`

`=>x∈{0;9}`

`b)(x-1).(x+2).(2x-4)=0` 

`TH1:x-1=0->x=1`

`TH2:x+2=0->x=-2`

`TH3:2x-4=0->x=2`

`=>x∈{1;-2;2}`

`c)24:(3x-2)=-3`

`3x-2=24:(-3)`

`3x-2=-8`

`3x=-6`

`x=-6:2`

`x=-3`

`d)-45:5.(-3-2x)=3`

`-9.(-3-2x)=3`

`-3-2x=-1/3`

`2x=-3+1/3`

`2x=-8/3`

`x=-8/3 :2`

`x=-4/3`

Câu 1:

a) (-13).7

= -91

b) 8.(-9)

= -72

c) 245.(-2)

= - 490

d) (-61).(-5)

= 305

e) (-6).|-28|

= (-6).28

= -168

Câu 2:

a) x.(x - 9) = 0

⇒ x = 0 hoặc x - 9 = 0

TH1: x = 0

TH2: x - 9 = 0

        x = 9

Vậy x ∈ {0; 9}

b) (x - 1)(x + 2)(2x - 4) = 0

⇒ x - 1 = 0 hoặc x + 2 = 0 hoặc 2x - 4 = 0

TH1: x - 1 = 0 

        x = 1

TH2: x + 2 = 0

        x = -2

TH3: 2x - 4 = 0

        2x = 4

          x = 2

Vậy x ∈ {1; -2; 2}

c) 24:(3x - 2) = -3

          3x - 2 = -8

          3x = -6

            x = -2

Vậy x = -2

d) -45:5.(-3 - 2x) = 3

    -9.(-3 - 2x) = 3

         -3 - 2x = -$\frac{1}{3}$ 

              -2x = $\frac{8}{3}$ 

                  x = -$\frac{4}{3}$ 

Vậy x = -$\frac{4}{3}$ 

Chúc bạn học tốt