答：a+b=3两边平方：(a+b)²=9a²+2ab+b²=9a²+2*1.25+b²=9a²+b²=6.5(a-b)²=a²-2ab+b²=6.5-2*1.25=4所以：a-b=2或者a-b=-2所以：a²-b²=(a+b)(a-b)=3(a-b)...