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已知a的平方-5a+1=0 求a得平方除以(a的四次方+a的二次方+1)的值
人气:244 ℃ 时间:2019-10-11 09:58:20
解答
∵a²-5a+1=0 ∴a²=5a-1 a4=(5a-1)²=25a²-10a+1=25x(5a-1)-10a+1=115a-24
a²/(a4+a²+1)=(5a-1)/(115a-24 +5a-1 +1)=(5a-1)/(120a-24)=1/24因式分解(x+y)(x+y+2xy)+x的平方y的平方-1(x+y)(x+y+2xy)+x²y²-1=x²+2xy+y²+2x²y+2xy²+x²y²-1=(x²+2x²y+x²y²)+(2xy+2xy²)+(y²-1)=x²(y+1)²+2xy(y+1)+(y+1)(y-1)=(y+1)(xy²+x²+2xy+y-1)=(y+1){(xy²+xy)+(xy+y)+(x²-1)}=(y+1)(x+1)(xy+y+x-1)
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