已知a=根号2-1,先化简√a눀-2a+1⼀a눀-a+a-1⼀a눀-2a+1+4a눀-16⼀a눀-4a+4,再求值

2024-11-15 11:13:35
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回答(1):

因为a=√2-1,所以a-1=√2-2<0。√a²-2a+1/a²-a+a-1/a²-2a+1+4a²-16/a²-4a+4=√(a-1)²/a(a-1)+a-1/(a-1)²+4(a²-4)/(a-2)²=-(a-1)/a(a-1)+1/(a-1)+4(a+2)(a-2)/(a-2)²=-1/a+1/(a-1)+4(a+2)/(a-2)。

由题:1/a=√2+1,1/(a-1)=1/(√2-2)=-(√2+2)/2=-√2/2-1,(a+2)/(a-2)=(√2+1)/(√2-3)=-(√2+1)(√2+3)/7=-5/7-4/7√2,代入上式得:-√2-1-√2/2-1-20/7-16/7√2=-53/14√2-34/7