展开得：a2+2ab+b2=1 a2-2ab+b2=25,两式相加得 2（a2+b2）=26，得a2+b2=13两式相减得4ab=-24，得ab=-6
a²+b²= [(a+b)²+(a-b)²]/2 = (1+25)/2 = 13ab= [(a+b)²-(a-b)²]/4 = (1-25)/4 = -6
13 -6
