Question

八下数学期末测试计算题若x²y+xy²=30,xy=6,求x-y的值

Answer 1

因为x^2y＋xy^2＝30,

xy(x+y)=30,

xy＝6

x+y=5

所以(x+y)^2=x^2＋y^2+2xy=x^2＋y^2+12=25

所以x^2＋y^2=13

所以(x－y)^2=x^2＋y^2-2xy=13-12=1