Câu hỏi của Thảo Vy Nguyễn - Toán lớp 6 - Học toán với OnlineMath

cả 2 bài luôn à

a,(567-46)-(54+567)

=567-46+54-567

=567.(46+54)

=567.100

=56700

Mình không biết

7 ( x – 9 ) – 5 ( 6 – x ) = -6 + 11x

7x - 7.9 - 5.6 + 5x = -6 + 11x

7x - 63 - 30 + 5x = -6 + 11x

7x + 5x - 63 - 30 - 11x = -6

7x + 5x - 11x = -6 + 63 + 30

7x + 5x - 11x = 87

x ( 7 + 5 -11 ) = 87

x . 1 = 87

x = 87

\(7\left(x-9\right)-5\left(6-x\right)=-6+11x.\)

\(\left(7x-63\right)-\left(30-5x\right)=-6+11x\)

\(7x-63-30+5x=-6+11x\)

\(12x-93=-6+11x\)

\(12x-11x=93-6\)

\(x=87\)

a, Ta có: \(|-n+8|\ge0\forall n\)

\(\Rightarrow|-n+8|-21\ge-21\forall n\)

Hay: \(A\ge-21\forall n\)

Vậy: Min A = -21 tại \(|-n+8|=0\) \(\Rightarrow n=8\)

b,Ta có: \(-3|2x+50|\le0\forall x\)

\(\Rightarrow-21-3|2x+50|\le-21\forall x\)

Hay: \(B\le-21\forall x\)

Vậy: Max B =-21 tại \(-3|2x+50|=0\) \(\Rightarrow x=-25\)

=.= hk tốt!!

\(124+\left(13-16\right)=162-\left(x+162\right).\)

\(124+13-16=162-\left(x+162\right)\)

\(121=162-\left(x+162\right)\)

\(41=x+162\)

\(x=41-162=\left(-121\right)\)

124 + ( 13 – 16 ) = 162 – ( x + 162 )

124 + (-3)            = 162 - ( x + 162 )

121                      = 162 - ( x + 162 )

\(\Rightarrow\)162 - ( x + 162 ) = 121

         162 - x - 162      = 121

         ( 162 - 162 ) - x  = 121

               0      - x         = 121

                  - x              = 121

\(\Rightarrow\)           x              = -121

\(7\left(x-3\right)-5\left(3-x\right)=11x-5.\)

\(\left(7x-21\right)-\left(15-5x\right)=11x-5\)

\(7x-21-15+5x=11x-5\)

\(12x-36=11x-5\)

\(12x-11x=36-5\)

\(x=31\)

7 (x - 3) - 5 (3 - x) = 11x - 5

7x - 7.3 - 5.3 - 5x = 11x - 5

7x - 5x - 21 -15 = 11x - 5

2x - (21 + 15) = 11x - 5

2x - 36 = 11x - 5

2x - 11x = 36 - 5

-9x = 31

x = 31:(-9)

x = \(\frac{-31}{9}\)

3 . ( 5^x -1 ) - 2 = 70

3 . ( 5^x -1 )       = 70 + 2

3 . ( 5^x -1 )       = 72

      5^x -1           = 72 : 3

      5^x -1           = 24 

      5^x               = 24 + 1

       5^x              = 25

       5^x              = 5²

=>  x = 2

a, \(x+\left(x+1\right)+\left(x+2\right)+...+\left(x+90\right)=5450\)

\(\left(x+x+x+...+x\right)+\left(1+2+3+...+90\right)=5450\)

\(91x+4095=5450\)

\(91x=1355\)

\(x=\frac{1355}{91}\)

b, \(2^x+2^{x+1}+2^{x+2}=960-2^{x+3}\)

\(2^x+2^x.2+2^x.2^2+2^x.2^3=960\)

\(2^x\left(1+2+2^2+2^3\right)=960\)

\(2^x.15=960\)

\(2^x=64=2^6\)

\(\Rightarrow x=6\)