|a|=2,|b|=3
则a²=|a|²=4,b²=|b|²=9
a⊥b,所以a*b=0
3a+2b与λa-b垂直,则它们的数量积要为0
(3a+2b)(λa-b)
=3λa²+2λab-3ab-2b²
=3λa²-2b²
=3λ×4-2×9
=12λ-18
=0
λ=3/2