初一代数式求值数学题
\u95ee\u4e00\u9053\u521d\u4e00\u5965\u6570\u9898\uff08\u4ee3\u6570\u5f0f\u6c42\u503c\u7684\uff09\u628a2ab-b2=3\u6574\u4f53\u4e58\u4ee53
\u518d\u628a\u4e24\u5f0f\u76f8\u52a0\uff0c\u521a\u597d\u5c31\u662fa2+4ab-3b2
\u7b54\u6848\u662f27
1\u3001P=25*4x=100x
2\u3001Q=[(200-x)*30-4*1.5*x]*2=12000-72x
3\u3001\u5f53x=166\u65f6\uff0cP=16600,\u6240\u4ee5W=16600
\u56e0\u4e3a\u82e5\u5b89\u6392167\u4e2a\u4eba\u5236\u8863\uff0c\u90a3\u4e48\u5c31\u5b89\u639233\u4e2a\u4eba\u7ec7\u5e03\uff0c\u90a3\u4e48\u5c31\u7ec7\u51fa990\u7c73
\u800c167\u4eba\u5236\u8863\u9700\u89811002\u7c73\u5e03\uff0c\u56e0\u4e3a990\u7c73\u5c0f\u4e8e1002\u7c73\uff0c\u6240\u4ee5\u4e0d\u80fd\u5b89\u6392167\u4eba\u5236\u8863\u3002
PS:\u8fd9\u4e9b\u662f\u6211\u81ea\u5df1\u505a\u7684\uff0c\u4ec5\u4f9b\u53c2\u8003\u3002
则有m+2=0，n-1=0，得m=-2，n=1，
故m+2n=0
0
m+2=0
n-1=0
m=-2
n=1
m+2n=0
m=-2，n=1
m+2n=-2+2=0
|m+2|+(n-1)的平方=0
m+2=0, m=-2
n-1=0,n=1
m+2n=0
|m+2|>-0;(n-1)^2>=0
m=-2,n=1
m+2n=0.
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