证明:因为 2/a+8/b=(2/a+8/b)×1
=(2/a+8/b)(a+b)
=2b/a+8a/b+10
=(2b²+8a²)/ab+10
=2(b²+(2a)²)/ab+10
≥2(2(b×2a))/ab+10
≥8ab/ab+10
≥18
所以 2/a+8/b ≥18
证明:因为 2/a+8/b=(2/a+8/b)×1
=(2/a+8/b)(a+b)
=2b/a+8a/b+10
=(2b²+8a²)/ab+10
=2(b²+(2a)²)/ab+10
≥2(2(b×2a))/ab+10
≥8ab/ab+10
≥18
所以 2/a+8/b ≥18