Question

Tính:
a) 3.(2x-3)+5.(x+2)
b) 3x.(2x-8)+(6x-2).(5-x)
c) (x-3).(x+3)-(x-5)² 
d) (x-y)³-(x-y).(x²+xy+y²)

Answer 1

a) \(3\left(2x-3\right)+5\left(x+2\right)=6x-9+5x+10=11x+1\)

b) \(3x\left(2x-8\right)+\left(6x+2\right)\left(5-x\right)=6x^2-24x+30x-6x^2+10-2x=4x+10\)

c) \(\left(x-3\right)\left(x+3\right)-\left(x-5\right)^2=x^2-9-x^2+10x-25=10x-34\)

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

Answer 2

Tk :

Answer 3

a: Ta có: \(3\left(2x-3\right)+5\left(x+2\right)\)

\(=6x-9+5x+10\)

\(=11x+1\)

b: Ta có: \(3x\left(2x-8\right)-\left(6x-2\right)\left(x-5\right)\)

\(=6x^2-24x-6x^2+30x+2x-10\)

\(=8x-10\)

c: Ta có: \(\left(x-3\right)\left(x+3\right)-\left(x-5\right)^2\)

\(=x^2-9-x^2+10x-25\)

\(=10x-34\)

Answer 4

d: Ta có: \(\left(x-y\right)^3-\left(x-y\right)\left(x^2+xy+y^2\right)\)

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

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