左边平方
=2a+1+2b+1+2√(2a+1)(2b+1)
=2(a+b)+2+2√(2a+1)(2b+1)
=2+2+2√(2a+1)(2b+1)
(2a+1)(2b+1)=4ab+2(a+b)+1=4ab+2+1=4ab+3
√ab