﹣5x²＋ax＋bx²＋2x－5与x的取值无关,求a,b的值.思路写清楚 ,让我明白

﹣5x²＋ax＋bx²＋2x－5与x的取值无关,求a,b的值.思路写清楚 ,让我明白
﹣5x²＋ax＋bx²＋2x－5与x的取值无关,求a,b的值.思路写清楚 ,让我明白

﹣5x²＋ax＋bx²＋2x－5与x的取值无关,求a,b的值.思路写清楚 ,让我明白
原式=(b-5)x²+(a+2)x-5
与x的取值无关则所有含x的想系数为0
所以b-5=0,a+2=0
所以a=-2,b=5

﹣5x²＋ax＋bx²＋2x－5
= (-5+b)x^2 + (a+2)x -5
independent of x
=> coef. of x^2 and coef. of x =0
=> -5+b =0 and a+2=0
=> b=5 and a =-2