看本人秒杀:
解:∵a>0、b>0, a²-b²=2ab>0.∴a>b>0. a²=b²+2ab. a²-b²-2ab=0.两边同时除以a²得:(b/a)²+2(b/a)-1=0.由求根公式得(把b/a当成一个数):
b/a=(-2+2√2)/2=√2-1.
而:(a-b)/(a+b)=(a-b)²/(a²-b²)=(a²-2ab+b²)/2ab=(b²+2ab+b²-2ab)/2ab=2b²/2ab=b/a=√2-1.
看本人秒杀:
解:∵a>0、b>0, a²-b²=2ab>0.∴a>b>0. a²=b²+2ab. a²-b²-2ab=0.两边同时除以a²得:(b/a)²+2(b/a)-1=0.由求根公式得(把b/a当成一个数):
b/a=(-2+2√2)/2=√2-1.
而:(a-b)/(a+b)=(a-b)²/(a²-b²)=(a²-2ab+b²)/2ab=(b²+2ab+b²-2ab)/2ab=2b²/2ab=b/a=√2-1.