若多项式mx³+3nxy²-2x³-xy²+y中不含三次项,求2m+3n的值
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![若多项式mx³+3nxy²-2x³-xy²+y中不含三次项,求2m+3n的值](/uploads/image/z/5260804-52-4.jpg?t=%E8%8B%A5%E5%A4%9A%E9%A1%B9%E5%BC%8Fmx%26%23179%3B%2B3nxy%26%23178%3B-2x%26%23179%3B-xy%26%23178%3B%2By%E4%B8%AD%E4%B8%8D%E5%90%AB%E4%B8%89%E6%AC%A1%E9%A1%B9%2C%E6%B1%822m%2B3n%E7%9A%84%E5%80%BC)
若多项式mx³+3nxy²-2x³-xy²+y中不含三次项,求2m+3n的值
若多项式mx³+3nxy²-2x³-xy²+y中不含三次项,求2m+3n的值
若多项式mx³+3nxy²-2x³-xy²+y中不含三次项,求2m+3n的值
mx³+3nxy²-2x³-xy²+y
=(mx³-2x³)+(3nxy²-xy²)+y
=(m-2)x³+(3n-1)xy²+y
不含三次项,则有
m-2=0,3n-1=0
∴m=2,n=1/3
∴2m+3n
=2×2+3×(1/3)
=4+1
=5
mx³+3nxy²-2x³-xy²+y
=x³(m-2)+xy²(3n-1)+y
m-2=0
3n-1=0
m=2
n=1/3