几道搞死人的数学题M的平方加M减一等于0 求M的3方加2个M的平方加2005的值就是2 3 2M +M-1=0 问 M

MM^2 + M - 1 = 0
求 M^3 + 2M^2 + 2005
M^2 + M - 1 = 0
所以 M^2 = 1-M
M^3 = M^2 * M = (1-M)M = M - M^2 = M - (1-M) = 2M -1
M^3 + 2M^2 + 2005
= (2M-1) + 2(1-M) + 2005
= 2006
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方法二：
M^3 + 2M^2 + 2005
=M^3 + M^2 - M + M^2 + M + 2005
=M(M^2 + M - 1) + M^2 + M -1 + 2006
=2006