【初2】几道数学题目````高手速度做答```````

题目

【初2】几道数学题目````高手速度做答```````
1'分解固式(1-a)mn+a-1=
2'若18x^2+19x+m=(9x+5)(2x+n),则m=?n=?
3'若关于x的三次二项式2x^2+mx+n因式分解的结果为(2x-1)(x+1/4),求m,n的植.
4'两个小孩的年龄分别是x,y,已知x^2+xy=99,求这两个孩子的年龄.(过程)尽量让我懂哈````!
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答案

1.提取公因式(1-a)mn+a-1 =(1-a)mn-(1-a) =(1-a)(mn-1) 2 .18x^2+19x+m =(9x+5)(2x+n) =18x^2+(10+9n)x+5n 等号两边对应的各项系数及常数项相等 所以 :19=10+9n m=5n 解得n=1,m=5 3 .(2x-1)(x+1/4)=2x^2+x*1/2-x-(1/...