Rút gọn biểu thức:

A=\(2x\left(x-2\right)-x\left(2x-3\right)\)

B=\(\left(x-1\right)\left(2x+1\right)-\left(x^2-2x-1\right)\)

C=\(\left(x+y\right)\left(x^2-xy+y^2\right)-x^3\)

D=\(\left(12x-3\right)\left(x+4\right)-x\left(2x+7\right)\)

E=\(\left(2x+y\right)\left(4x^2-2xy+y^2\right)\)

Chứng minh rằng:

a) \(\left(a+b\right)\left(a+c\right)+\left(c+a\right)\left(c+b\right)=2\left(b+a\right)\left(b+c\right)\)biết \(a^2+c^2=2b^2\).

b) \(a\left(a+2\right)-a\left(a-7\right)\left(a-5\right)⋮7\)với mọi giá trị nguyên của a.

chứng minh rằng giá trị ko phụ thuộc vào biến y

y^4 -( y^2 - 1)( y^2 +1)

BT3/6. Tìm x, biết

a/ 2x(12x-5)-8x(3x-1)=30

b/3x(3-2x)+6x(x-1)=15

Cho a3 + b3 + c3 = 0

CMR a3b3 + 2b3c3 + 3a3c3 \(\le\)0

Cho 2aa + bb = 3cc

Tính: 2015a-b + 2016b-c + 2017c-a

a) (x+2).(x-5) > 0

b) (x-3).(x+4) < 0

a,5(x-2)+3x (x-2)=0

b,2/3+5/2:x=2/4

c,2x(x-1/7)=0

d,11/12-(2/5+x)=2/3

e,3/4+1/4:x=2/5

g,2/3x+5/7=3/10

Tìm x:

a) \(\dfrac{2}{3}\) - \(\dfrac{1}{3}\) . ( x - \(\dfrac{3}{2}\) ) - \(\dfrac{1}{2}\) . ( 2x + 1 ) = 5

b) ( x + \(\dfrac{1}{2}\) ) . ( \(\dfrac{3}{4}\) - x ) = 0

c) \(\dfrac{2x-1}{-3+2}\) = 0

Tìm x, biết

a) x(2x-7)-4x+14=0

b) (2x+5)(3x-1)-(2x+5)=0

c) \(\left(2x-3\right)^2-6x+9=0\)