(1)已知2m=3,32n=6,求23m-10n;(2)若(x2+nx+3)(x2-3x+m)的乘积中不含x2和x3项,求m、n的值.
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(1)已知2m=3,32n=6,求23m-10n; (2)若(x2+nx+3)(x2-3x+m)的乘积中不含x2和x3项,求m、n的值. |
答案
(1)23m-10n=23m÷210n=(2m)3÷(25)2n=(2m)3÷322n=(2m)3÷(32n)2, ∵2m=3,32n=6, ∴原式=33÷62 =27÷36 =;
(2)(x2+nx+3)(x2-3x+m) =x4+nx3+3x2-3x3-3nx2-9x+mx2+mnx+3m =x4+(n-3)x3+(3-3n+m)x2+(mn-9)x+3m, ∵乘积中不含x2和x3项, ∴n-3=0,3-3n+m=0, 解得:m=6,n=3. |
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