根号下a平方减2a减8 加绝对值2a方减3a减20等于0
问题描述：
根号下a平方减2a减8 加绝对值2a方减3a减20等于0
答
√(a²-2a-8)+|2a²-3a-20|=0,
=> a²-2a-8=0, 2a²-3a-20=0,
a²-2a-8=0, => (a-4)(a+2)=0, =>a=4或-2
2a²-3a-20=0, => (2a+5)(a-4)=0, => a=4或-2.5
=> a=4
答
√(a²-2a-8)+|2a²-3a-20|=0,则 a²-2a-8=0,2a²-3a-20=0,由a²-2a-8=0 (a-4)(a+2)=0得a=4或a=-2由2a²-3a-20=0(2a+5)(a-4)=0,得 a=4或-2.5所以a=4