B

Chọn B

a)25,52 - x : 2,5 = 4,61

      x : 2,5 = 25,52 - 4,61

      x ; 2,5 =  20,91

     x      = 20,91 x 2,5 

     x      = 52,275

b) 12,6 - x + 4,5 = 4,61

 12,6 - x      = 4,61 - 4,5 

 12,6 - x      = 0,11

     x       = 12,6 - 0,11

     x       = 12,49

c) x - 75/100 = 125/100 + 9/10 

 x -  0,75 = 1,25 + 0,9 

 x -  0,75 = 2,15

 x      = 2,15 + 0,75 

 x      = 2,90

tìm x , biết :

a . 1,5 . x + 2,5 = 1

\(1,5.x=-1,5\)

\(x=\dfrac{-1,5}{1,5}\)

\(x=-1\)

b . ( 0,5 . x - 1,3 ) : 0,5 = -1,7

\(0,5.x-1,3=-0,85\)

\(0,5x=-2,15\)

\(x=\dfrac{-2,15}{0,5}\)

\(x=-4,3\)

c . 1,75 .x - 1,5 . x = 0,84

\(x\left(1,75-1,5\right)=0,84\)

\(x.0,25=0,84\)

\(x=3,36\)

d . x + 75% . x + 125% = 1

\(x+\dfrac{75}{100}.x+\dfrac{125}{100}=1\)

\(x+\dfrac{3}{4}.x+\dfrac{5}{4}=1\)

\(x+\dfrac{3}{4}.x=-\dfrac{1}{4}\)

\(x.\left(1+\dfrac{3}{4}\right)=-\dfrac{1}{4}\)

\(x.1,75=-\dfrac{1}{4}\)

\(x=-\dfrac{1}{7}\)

e . x - 25% .x + 75% = 1

\(x-\dfrac{25}{100}.x+\dfrac{75}{100}=1\)

\(x-\dfrac{1}{4}.x+\dfrac{3}{4}=1\)

\(x-\dfrac{1}{4}.x=\dfrac{1}{4}\)

\(x.\left(1-\dfrac{1}{4}\right)=\dfrac{1}{4}\)

\(x.\dfrac{3}{4}=\dfrac{1}{4}\)

\(x=\dfrac{1}{3}\)

f . | x - 1,5 | = 2,37

TH1 : \(x-1,5=2,37\)

\(x=2,37+1,5\)

\(x=3,87\)

TH2 : \(x-1,5=-2,37\)

\(x=-2,37+1,5\)

\(x=-0,87\)

(-125) + 225 - (-125) + 75 =(-125)+225+125+75=225+75+125-125=300

50

50

chưa chắc

a/19.5

b/0.96

c/1.6

d/-63.952

a) \(A=125\left(-24\right)+24.225\)

\(=24\left[\left(-125\right)+225\right]\)

\(=24.100=2400\)

b) \(B=26\left(-125\right)-125\left(-36\right)\)

\(=125\left[\left(-26\right)-\left(-36\right)\right]\)

\(=125.10=1250\)

c) \(C=25\left(75-45\right)-75\left(45-25\right)\)

\(=25.75-25.45-75.45-75.25\)

\(=\left(25.75-75.25\right)-25.45-75.45\)

\(=-25.45-75.45\)

\(=45\left(-25-75\right)\)

\(=45\left(-100\right)=-4500\)

A = 125(125 + 150) + 75²

A = 34375 + 75²

A = 34375 + 5652

A = 40000

\(A=125\left(125+150\right)+75^2\)

\(=125^2+125.150+75^2\)

\(=\left(125+75\right)^2\)

\(=200^2=40000\)