Question

已知a=3+2根号2，b=3－2根号2,求a的2次方b－ab的2次方

急急呀

Answer 1

解：
∵a=3+√2，b=3-√2
∴a-b=2√2，ab=7
∴a²b-ab²=ab(a-b)=7*(2√2)=14√2

Answer 2

已知a=3+2根号2，b=3－2根号2,求a的2次方b－ab的2次方
a²=(3+√2 )²=9+2*3*√2+(√2 )²=11+6 √2
(b－ab)²=[3-√2 -(3+√2 )(3-√2 )]²=[3-√2-(3²-√2 ²)]²=(3-√2 -9+2)²
=(4-√2)²=16-2*4*√2+√2²=18-8√2

Answer 3

a平方=17+12√2
b-ab的平方=15-10√2

Answer 4

解：ab=(3+2√2)(3-2√2)=9-8=1
所以：a²b-ab=ab*(a-1)
=1*(3+2√2-1)
=2+2√2