Bài 12: Tính chất của phép nhân

a)

\(4\left(x-1\right)-\left(3x+2\right)=16\)

=> 4x - 4 - 3x - 2 = 16

=> x - 6 = 16

=> x = 22

Vậy .......

b)

\(7\left(x-5\right)+5\left(15-x\right)=130\)

=> 7x - 35 + 75 - 5x = 130

=> 2x + 40 = 130

=> 2x = 90

=> x = 45

Vậy........

c)

\(30\left(x-2\right)-6\left(x-5\right)-22x=100\)

=> 30x - 60 - 6x + 30 - 22x = 100

=> 2x - 30 = 100

=> 2x = 130

=> x = 65

Vậy.....

d) \(x-17+x=x-23\)

=> 2x - 17 = x - 23

=> x = -6

Vậy .......

a) 4(x-1)-(3x+2)=16 b)7(x-5)+5(15-x)=130

<=>4x-4-3x-2=16 <=>7x-35+75-5x=130

<=>x-6=16 <=>2x+40=130

<=>x=22 <=>2x=90

<=>x=45

c) 30(x- 2 ) - 6( x - 5 ) - 22x = 100 d) x-17+x=x-23

<=>30x-60-6x+30-22x=100 <=>2x-x=-23+17

<=>2x-30=100 <=>x=-6

<=>2x=130

<=>x=65

a) 4(x-1)-(3x+2)=16

<=>4x-4-3x-2=16

<=>x-6=16

<=>x=22

c) 30(x- 2 ) - 6( x - 5 ) - 22x = 100

<=>30x-60-6x+30-22x=100

<=>2x-30=100

<=>2x=130

<=>x=65

b)7(x-5)+5(15-x)=130

<=>7x-35+75-5x=130

<=>2x+40=130

<=>2x=90

<=>x=45

d) x-17+x=x-23

<=>2x-x=-23+17

<=>x=-6

<=>2x=130

<=>x=65

a) (-125).(-13).(-a) , với a =8

Theo đề bài ta có

(-125).(-13).(-8)

= (-125).(-8).(-13)

=1000.(-13)

= (-13000)

b) (-1).(-2).(-3).(-4).(-5).b , với b=20

Theo đề bài ta có

(-1).(-2).(-3).(-4).(-5).20

=[ (-1).20].[ (-5).(-2)].[ (-3).(-4)]

=(-20).10.12

=(-200).12

= (-2400)

\(29\cdot\left(19-13\right)-19\cdot\left(29-13\right)\\ =29\cdot19-29\cdot13-19\cdot29+19\cdot13\\ =\left(29\cdot19-19\cdot29\right)+\left(19\cdot13-29\cdot13\right)\\ =0+13\left(19-29\right)\\ =13\cdot\left(-10\right)\\ =-130\)

31.(-18)+31.(-81)-13

=31.(-18+(-81))-13

=31.(-99)-13

=-3069-13

=-3082

Bài 1 . Tính

a, 72 : ( -6 . 2 + 4 )

= 72 : ( -12 + 4 )

= 72 : -8

= -9

b, -3 . 7 - 4 . ( -5 ) + 1

= -21 . ( -20 ) + 1

= 420 + 1

= 421

c, 18 - 10 : ( +2 )

= 18 - 5

= 13

a, 72 : ( -6 . 2 + 4 )

= 72 : ( -12 + 4 )

= 72 : -8

= -9

b, -3 . 7 - 4 . ( -5 ) + 1

= -21 . ( -20 ) + 1

= 420 + 1

= 421

c, 18 - 10 : ( +2 )

= 18 - 5

= 13

a)2.(50+35):(-20+3)

=(2.50+35.2):(-20+3)

=(100+70):(-17)

=170:(-17)

=-10

b)(-4).17+(-4).83-(-50)

=(-4).(17+83)-(-50)

=(-4).100-(-50)

=-400-(-50)

=-350

c)10.(-8)+(-10).(-8)

=(-80)+80

=0

a: \(\left(36-16\right)\cdot\left(-15\right)+16\cdot\left(-14-6\right)\)

\(=-15\cdot20+16\cdot\left(-20\right)=-20\cdot\left(-15+16\right)=-20\)

b: \(\left(-47\right)\cdot\left(-69\right)-\left(-31\right)\cdot47\)

\(=47\cdot69+31\cdot47\)

\(=47\cdot100=4700\)

c: \(38\cdot\left(-41\right)+59\cdot\left(-38\right)\)

\(=38\left(-41-59\right)\)

\(=-100\cdot38=-3800\)

\(-18.\left(-16+20\right)-26.\left(6-18\right)+16.\left(-18+20\right)\)

\(=\left(-18\right).4-26.\left(-12\right)+16.2\)

\(=-72+312+32\)

\(=272\)

\(\left(-3\right)\left(-x\right)=-9\\ \Leftrightarrow-x=\left(-9\right):\left(-3\right)\\ \Leftrightarrow-x=3\\ \Leftrightarrow x=-3\)

\(\left(-3\right)^x=-27\\ \Leftrightarrow\left(-3\right)^x=\left(-3\right)^3\\ \Leftrightarrow x=3\)

a) \(\left(-3\right).\left(-x\right)=-9\)

\(\Leftrightarrow-x=\left(-9\right):\left(-3\right)\)

\(\Leftrightarrow-x=3\)

\(\Leftrightarrow x=-3\)

b) \(\left(-3\right)^x=-27\)

\(\Leftrightarrow\left(-3\right)^x=\left(-3\right)^3\)

\(\Leftrightarrow x=3\)