Question

 lm giúp mik vs 

Answer 1

bài 1
a)
=(x+y-x+y)(x+y+x-y)
=2x.2y
=4xy
b)
B=(x+y-x+y)²=4y²
c)
=(x+y-x+y)[(x+y)²+(x+y)(x-y)+(x-y)²]-2y³
=2y(\(x^2+2xy+y^2+x^2-y^2+x^2-2xy+y^2\))-2y³
=\(2y\left(3x^2+y^2\right)-2y^3=6x^2y+2y^3-2y^3=6x^2y\)

Answer 2

Bài 3:

a: Ta có: \(A=\left(x+y\right)^2-\left(x-y\right)^2\)

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

=4xy

b: ta có: \(B=\left(a+b\right)^3+\left(a-b\right)^3-2a^3\)

\(=a^3+3a^2b+3ab^2+b^3+a^3-3a^2b+3ab^2-b^3-2a^3\)

\(=6ab^2\)

c: Ta có: \(C=9^8\cdot2^8-\left(18^4-1\right)\left(18^4+1\right)\)

\(=18^8-18^8+1\)

=1