∵(a+b)²+(a-b)²=(a²+b²+2ab)+(a²+b²-2ab)=2a²+2b²=11∴a²+b²=11/2∵(a+b)²-(a-b)²=(a²+b²+2ab)-(a²+b²-2ab)=a²+b²+2ab-a²-b²+2ab=4ab=3∴ab=3/4
(a+b)²+(a-b)²=a²+b²+2ab+a²+b²-2ab=2a²+2b²=11 ->a²+b²=11/2(a+b)²-(a-b)²=a²+b²+2ab-a²-b²+2ab=4ab=3 -> ab=3/4