x+y=4/15 ①4.8x+12y=1.88 ②x+y=16 ①4.5*x/60+12*y/60=1880/1000
(x*x+y*y)(x*x+y*y)-(x*x+y*y)=12 求x*x+y*y等于多少
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[x(x-y)-y(x-y)+(x+y)(x-y)]÷2x其中x=2012 y=2013