若x=3+1,则y=2x5-4x4-x3-6x2-6的值为_.
若x=
+1,则y=2x5-4x4-x3-6x2-6的值为______.
3 |
数学人气:663 ℃时间:2019-10-31 23:22:26
优质解答
由x=3+1得3=(x-1)2,∴y=2x5-4x4-x3-6x2-6=2x3(x2-2x+1)-2x3-x3-6x2-6=2x3(x-1)2-3x3-6x2-6=2x3×3-3x3-6x2-6=3x3-6x2-6=3x(x2-2x)-6=3x(x2-2x+1)-3x-6=3x(x-1)2-3x-6=3x•3-3x-6=9x-3x-6=6x-6=6(x-1)...
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