Question

Efetue: a) (x – 1) (x + 2)
b) (x + 2y)ao quadrado– (x – y)ao quadrado

Answer 1

a) (x-1).(x+2)= x²+2x-1x -2= x²+ 1x -2= x²+x-2

b) (x+2y)² - (x-y)²=

(x+2y).(x+2y) -[ (x-y).(x-y)]=

x²+2xy+2xy+4y²- [ x²-xy-xy+y²]=

x²+4xy +4y²- [x²-2xy+y²]=

x²+4xy+4y²-x²+2xy-y²=

4xy+2xy +4y²-y²=

6xy +3y²