先合并同類項,再求出的a,b值,最后求出代數(shù)式3a^2-2b^2-(2a^2-ab+3b^2)的值
(2x^2+ax-y-b)-(2bx^2-3x-5y-1)
=2x^2+ax-y-b-2bx^2+3x+5y+1
=2x^2-2bx^2+ax+3x+5y-y-b+1
=(2-2b)x^2+(a+3)x+5y-y-b+1
代數(shù)式(2x^2+ax-y-b)-(2bx^2-3x-5y-1)的值與字母x所取的值無關
即2-2b=0,a+3=0
a=-3
b=1
3a^2-2b^2-(2a^2-ab+3b^2)
=3a^2-2b^2-2a^2+ab-3b^2
=3a^2-2a^2-2b^2-3b^2+ab
=a^2-5b^2+ab
=(-3)^2-5*1^2+(-3)*1
=9-5-3
=1
=