干什么?解方程吗?
确认是x²-2√5-15=0?
还是x²-(2√5)x-15=0?
1、如果是前者:
x²-2√5-15=0
x²=15+2√5
x²=±√(15+2√5)
x1=√(15+2√5)
x2=-√(15+2√5)
2、如果是后者:
x²-(2√5)x-15=0
x²-(2√5)x+(√5)²-(√5)²-15=0
(x-√5)²-20=0
(x-√5)²=20
x-√5=±√20
x-√5=±2√5
x=√5±2√5
x1=3√5、x2=-√5
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