Question

因式分解 用简便方法计算因式分解1.(a-2)(a-3)+5a-42 2.x^2-(y^2-2y+1)用简便方法计算1.

Answer 1

1. (a-2)(a-3)+5a-42

=a²-5a+6+5a-42

=a²-36

=(a-6)(a+6)

2. x^2-(y^2-2y+1)

=x^2-(y-1)^2

=(x-y+1)(x+y-1)

1. 2009^2-2008*2010

=2009^2-(2009-1)(2009+1)

=2009^2-(2009^2-1)

=2009^2-2009^2+1

=1

2. 999^2+999*2+1

=(999+1)^2

=1000^2

=1000000