|b|^2-2√2|b|-6=0,|b|等于多少?怎么算的快?
问题描述:
|b|^2-2√2|b|-6=0,|b|等于多少?怎么算的快?
答
|b|^2-2√2|b|-6=0,
(|b|-3√2)(|b|+√2)=0
|b|=3√2,|b|=-√2(舍去)
|b|=3√2