已知a b c为△ABC的三边,且a²—2bc=b²—2ac,试判断△ABC的形状.
人气:249 ℃ 时间:2019-08-22 09:15:30
解答
a²-2bc=b²-2ac
移项得a²+2ac=b²+2bc
两边加c²
a²+2ac+c²=b²+2bc+c²
(a+c)²=(b+c)²
因为a,b,c>0
所以a+c=b+c
a=b
所以三角形是等腰三角形
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