已知(2x²+ax-y+b)-(2bx的平方-3x+5y-1)的值与字母x的取值无关.求3(a²-ab-b²)-(4a²+ab+b²)的值.
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已知(2x²+ax-y+b)-(2bx的平方-3x+5y-1)的值与字母x的取值无关.求3(a²-ab-b²)-(4a²+ab+b²)的值.
已知(2x²+ax-y+b)-(2bx的平方-3x+5y-1)的值与字母x的取值无关.
求3(a²-ab-b²)-(4a²+ab+b²)的值.
已知(2x²+ax-y+b)-(2bx的平方-3x+5y-1)的值与字母x的取值无关.求3(a²-ab-b²)-(4a²+ab+b²)的值.
(2x²+ax-y+b)-(2bx²-3x+5y-1)
=2x²+ax-y+b-2bx²+3x-5y+1
=(2-2b)x²+(a+3)x+(-y-5y)+b+1
∵代数式的值与字母X的取值无关,
∴2-2b=0, a+3=0
∴b=1, a=-3
3(a²-ab-b²)-(4a²+ab+b²)
=3a²-3ab-3b²-4a²-ab-b²
=-a²-4ab-4b²
=-(-3)²-4×(-3)×1-4×1²
=-9-(-12)-4
=-9+12-4
=-1
(2x²+ax-y+b)-(2bx的平方-3x+5y-1)
=2x²+ax-y+b-2bx²+3x-5y+1
=(2-2b)x²+(a+3)x-6y+b+1 的值与字母x的取值无关,则:
2-2b=0, a+3=0
a= -3, b=1
3(a²-ab-b²)-(4a²+ab+b²...
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(2x²+ax-y+b)-(2bx的平方-3x+5y-1)
=2x²+ax-y+b-2bx²+3x-5y+1
=(2-2b)x²+(a+3)x-6y+b+1 的值与字母x的取值无关,则:
2-2b=0, a+3=0
a= -3, b=1
3(a²-ab-b²)-(4a²+ab+b²)
=3a²-3ab-3b²-4a²-ab-b²
= -a²-4ab-4b²
= -(-3)²-4x(-3)x1-4x1
= -9+12-4
= -1
收起
解
原式=2x^2+ax-y+b-2bx^2+3x-5y+1
=(2x^2-2bx^2)+(ax+3x)+(-y-5y)+(b+1)
=(2-2b)x^2+(a+3)x-6y+b+1
所以
2-2b=0且a+3=0
解得
b=1,a=-3
代入所给代数式得
3a^2-3ab-3b^2-4a^2-ab-b^2
=-a^2-4ab-4b^2
=-9+12-4
=-1