(2x-1)²-9(x+1)²=(2x-1)^2-[3(x+1)]^2
=[(2x-1)+3(x+1)][(2x-1)-3(x+1)]
=(5x+2)(-x-4)
=-(5x+2)(x+4)
100²-99²+98²-97²+…+2²-1²
=(100+99)(100-99)+(98+97)(98-97)+……(2+1)(2-1)
=100+99+98+97+……+2+1
=(100+1)*100/2
=5050
(2x-1)²-9(x+1)²=(2x-1)^2-[3(x+1)]^2
=[(2x-1)+3(x+1)][(2x-1)-3(x+1)]
=(5x+2)(-x-4)
=-(5x+2)(x+4)
100²-99²+98²-97²+…+2²-1²
=(100+99)(100-99)+(98+97)(98-97)+……(2+1)(2-1)
=100+99+98+97+……+2+1
=(100+1)*100/2
=5050