(x^2+ax-y+b) - (bx^2-3x+6y-3)
= (1-b)x^2+(a+3)x-.
差的值与字母x无关：
1-b=0,a+3=0
a=-3,b=1
3（a^2-2ab-b^2)+(4a^2+ab+b^2)
= 3a^2-6ab-3b^2+4a^2+ab+b^2
= 7a^2-5ab-2b^2
= (7a+b)(a-2b)
= (7*(-3)+1)(-3-2*1)
= -20*(-5)
= 100