Question

ĐỀ BÀI: RÚT GỌN BIỂU THỨC

a) (x-2) . (x^2-5x++1) - x(x^2+11)

b) (x-1). (x^2+x+1) + (x^3-2)

c) (x-y). ( x+y) - 2x(x-y)

MONG MN GIÚP MÌNH VỚI Ạ!

THANKS!!!!

Answer 1

a) \(\left(x-2\right)\left(x^2-5x+1\right)-x\left(x^2+11\right)\)

\(=x\left(x^2-5x+1\right)-2\left(x^2-5x+1\right)-x\left(x^2+11\right)\)

\(=x^3-5x^2+x-2x^2+10x-2-x^3-11x\)

\(=-7x^2-2\)

b) \(\left(x-1\right)\left(x^2+x+1\right)+x^3-2\)

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

\(=x^3+x^2+x-x^2-x-1+x^3-2\)

\(=2x^3-3\)

c) \(\left(x-y\right)\left(x+y\right)-2x\left(x-y\right)\)

\(=x\left(x+y\right)-y\left(x+y\right)-2x\left(x-y\right)\)

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

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

Answer 2

a, \(\left(x-2\right)\left(x^2-5x+1\right)-x\left(x^2+11\right)\)

\(=x^3-7x^2+11x-2-x^3-11x=-7x^2-2\)

b, \(\left(x-1\right)\left(x^2+x+1\right)+\left(x^3-2\right)\)

\(=x^3-1+x^3-2=2x^3-3\)

c, \(\left(x-y\right)\left(x+y\right)-2x\left(x-y\right)\)

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