若使多项式2x³-8x²+x-1与多项式3x²+2mx²-5x+3相加后不含二次项,则m等于A.2 B.-2 C.4 D.8 哪一个?
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![若使多项式2x³-8x²+x-1与多项式3x²+2mx²-5x+3相加后不含二次项,则m等于A.2 B.-2 C.4 D.8 哪一个?](/uploads/image/z/1002076-52-6.jpg?t=%E8%8B%A5%E4%BD%BF%E5%A4%9A%E9%A1%B9%E5%BC%8F2x%26%23179%3B-8x%26%23178%3B%2Bx-1%E4%B8%8E%E5%A4%9A%E9%A1%B9%E5%BC%8F3x%26%23178%3B%2B2mx%26%23178%3B-5x%2B3%E7%9B%B8%E5%8A%A0%E5%90%8E%E4%B8%8D%E5%90%AB%E4%BA%8C%E6%AC%A1%E9%A1%B9%2C%E5%88%99m%E7%AD%89%E4%BA%8EA.2+B.-2+C.4+D.8+%E5%93%AA%E4%B8%80%E4%B8%AA%EF%BC%9F)
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若使多项式2x³-8x²+x-1与多项式3x²+2mx²-5x+3相加后不含二次项,则m等于A.2 B.-2 C.4 D.8 哪一个?
若使多项式2x³-8x²+x-1与多项式3x²+2mx²-5x+3相加后不含二次项,则m等于
A.2 B.-2 C.4 D.8 哪一个?
若使多项式2x³-8x²+x-1与多项式3x²+2mx²-5x+3相加后不含二次项,则m等于A.2 B.-2 C.4 D.8 哪一个?
(2x³-8x²+x-1)+(3x³+2mx²-5x+3)
=2x³-8x²+x-1+3x³+2mx²-5x+3
=(2+3)x³+(-8+2m)x²+(1-5)x-1+3
不含二次项,即二次项系数为0
则-8+2m=0
解得m=4
选C
你提抄错了!
-8+3+2m=0
m=5/2
若使多项式2x³-8x²+x-1与多项式3x²+2mx²-5x+3相加后不含二次项,
则 -8+(3+2m)=0,m=5/2
2x³-8x²+x-1+3x³+2mx²-5x+3
=5x³-8x²+2mx²-4x+2
由于两式之和不含二次项,所以-8x²+2mx²=0
-8+2m=0
m=4
要是按你给的条件,m=2.5