当x-y=5时,求x的平方-y的平方+5x+5y+2009的值?
问题描述:
当x-y=5时,求x的平方-y的平方+5x+5y+2009的值?
答
x^2-y^2+5x+5y+2009=(x-y)(x+y)+5(x+y)+2009=(x+y)(x-y-5)+2009=0+2009=2009
当x-y=5时,求x的平方-y的平方+5x+5y+2009的值?
x^2-y^2+5x+5y+2009=(x-y)(x+y)+5(x+y)+2009=(x+y)(x-y-5)+2009=0+2009=2009