#maianhhappy

bài 1 tính giá trị biểu thức

( - 25 ) nhân ( -3 ) nhân x với x = 4

\(\left(-25\right).\left(-3\right).4\)

\(=\left(-25\right).4.\left(-3\right)\)

\(=-100.\left(-3\right)=300\)

( -1 ) nhân ( -4 ) nhân 5 nhân 8 nhân y với y =25

\(\left(-1\right).\left(-4\right).5.8.25\)

\(=4.5.8.25=4.25.5.8\)

\(=100.40=40000\)

( 2ab mũ 2 ) : c với a =4 ; b= -6 ; c =12

\(\left(2.4.\left(-6\right)\right)^2:12\)

\(=\left(-48\right)^2:12\)

\(=2304:12=192\)

[ ( -25 ) nhân ( - 27 ) nhân ( -x ) ] : y với x = 4 ; y = -9

\(\left[\left(-25\right).\left(-27\right).\left(-4\right)\right]:-9\)

\(=-2700:\left(-9\right)\)

\(=300\)

(a mũ 2 _ b mũ 2) : ( a + b ) nhân ( a _ b ) với a + 5 , b = -3

\(\left(5^2-\left(-3\right)^2\right):\left(5-3\right).\left(5+3\right)\)

\(=16:2.8\)

\(=8.8=64\)

bài 2 tìm x

( 2x _ 5 ) + 17 = 6

\(2x-5=-11\)

\(2x=-6\)

\(x=-3\)

10 _ 2 ( 4 _ 3x ) = - 4

\(2.\left(4-3x\right)=14\)

\(4-3x=7\)

\(3x=-3\)

\(x=-1\)

- 12 + 3 ( -x + 7 ) = -18

\(3\left(-x+7\right)=-6\)

\(-x+7=-2\)

\(-x=-9\)

\(x=9\)

24 : ( 3x _ 2 ) = -3

\(3x-2=-8\)

\(3x=-6\)

\(x=-2\)

- 45 : 5 nhân ( -3 _ 2x ) = 3

\(5.\left(-3-2x\right)=-15\)

\(-3-2x=-3\)

\(2x=0\)

\(x=0\)

\(5.\left(x+35\right)=515\)

     \(x+35=515:5\)

     \(x+35=103\)

     \(x=103-35\)

 \(\Rightarrow x=68\)

\(\left(x+40\right).15=75.12\)

\(\Rightarrow\left(x+40\right)=5.12\)[ rút gọn theo t/c đẳng thức ]

\(x+40=60\)

\(x=20\)

trả lời giùm mình mấy câu kia với

ai nhNH MK K

tra loi nhanh ho mk voi

\(A=\frac{1}{2}+\frac{1}{6}+\frac{1}{12}+\frac{1}{20}+\frac{1}{30}+\frac{1}{42}\)

    = \(\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+\frac{1}{5.6}+\frac{1}{6.7}\)

      = \(1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+\frac{1}{5}-\frac{1}{6}+\frac{1}{6}-\frac{1}{7}\)

      = \(1-\frac{1}{7}\)

      =   \(\frac{7}{7}-\frac{1}{7}\)

        = \(\frac{6}{7}\)

2) \(\frac{7}{4}-x.\frac{4}{3}=\frac{5}{19}\)

              \(x.\frac{4}{3}=\frac{7}{4}-\frac{5}{19}\)

         \(x.\frac{4}{3}=\frac{133}{76}-\frac{20}{76}\)

\(x.\frac{4}{3}=\frac{113}{76}\)

      \(x=\frac{113}{76}:\frac{4}{3}\)

      \(x=\frac{399}{304}\)

VẬY \(x=\frac{399}{304}\)

b) \(\left(x+\frac{3}{4}\right).\frac{5}{7}=\frac{10}{9}\)

      \(\left(x+\frac{3}{4}\right)=\frac{10}{9}:\frac{5}{7}\)

     \(x+\frac{3}{4}=\frac{14}{9}\)

              \(x=\frac{14}{9}-\frac{3}{4}\)

               \(x=\frac{29}{36}\)

Vậy \(x=\frac{29}{36}\)

c) \(x.\frac{1}{2}+\frac{3}{2}.x=\frac{4}{5}\)

\(x.\left(\frac{1}{2}+\frac{3}{2}\right)=\frac{4}{5}\)

\(x.2=\frac{4}{5}\)

     \(x=\frac{4}{5}:2\)

      \(x=\frac{2}{5}\)

Vậy \(x=\frac{2}{5}\)

Chúc bạn học tốt !!!

dung roi,cam on ban nhieu

(12 X 15 -x) X 1/4 = 120

12 X 15 -x = 120 : 1/4

12 X 15 -x = 30

12 X 15 = 30+ x

180 = 30 + x

x =180 : 30

x = 6

\(\left(12\times15-x\right)\times\frac{1}{4}=120\)

\(\Rightarrow\left(180-x\right)\times\frac{1}{4}=120\)

\(\Rightarrow180-x=120:\frac{1}{4}\)

\(\Rightarrow180-x=480\)

\(\Rightarrow x=180-480\)

\(\Rightarrow x=-300\)

Vậy x = -300

_Chúc bạn học tốt_

`A=1,5xx2,9+0,5xx21+1/100 xx15-2`

`A=4,35+10,5+0,15-2`

`A=14,85+0,15-2`

`A=15-2=13`

\(a=1,5\times2,9+0,5\times21+\dfrac{1}{100}\times15-2\)

\(a=1,5\times2,9+0,5\times21+0,01\times15-2\)

\(a=4,35+10,5+0,15-2\)

\(a=13\)

`A = 1,5 xx 2,9 0,5 xx 21 + 1/100 xx 15 - 2`

`= 4,35 + 10,5 + 0,15 - 2`

`= 15 - 2`

`= 13`.

\(\frac{10}{3}.x+\frac{67}{4}=\frac{53}{4}\)

\(\frac{10}{3}.x=\frac{53}{4}-\frac{67}{4}\)

\(\frac{10}{3}.x=-\frac{7}{2}\)

\(x=-\frac{7}{2}:\frac{10}{3}\)

\(x=-\frac{21}{20}\)

a,(5.9.x-25):12=0

  (45.x-25):12=0

 (45.x-25)     =0x12

(45.x-25)=0

45.x=0+25

45.x=25

x=25:45

x=5/9

b,30.(x-28)=120

        (x-28)=120:30

        (x-28)=4

         x=4+28

        x=32

c'84-4.(2.x+1)=48

       4.(2.x+1)=84-48

        4.(2.x+1)=36

             (2.x+1)=36:4

            (2.x+1)=9

           2.x=9-1

            2.x=8

            x=8:2

             x=4

d,[(x+32)-15].2=60

  [(x+32)-15]=60:2

[(x+32)-15]=30

 (x+32)=30+15

(x+32)=45

x=45-32

x=13

a,

(5.9.x-15):12=0

45x-15=0

45x=0+15=15

x=45:15

x=3

b, 

30(x-28)=120

x-28=120:30=4

x=4+28

x=32

c,

84-4(2.x+1)=48

4(2.x+1)=84-48=36

2x+1=36:4=9

2x=9-1=8

x=8:2

x=4

d,

[(x+32)-15].2=60

(x+32)-15=60:2=30

x+32=30+15=45

x=45-32

x=13