Question

已知x+y＝7 ,xy＝10, 求下列各式的值： （1）x⒉+y⒉ (2)(x-y)⒉ (2是平方)

Answer 1

已知x+y＝7 ,xy＝10, 求下列各式的值： （1）x⒉+y⒉ (2)(x-y)⒉
(1)x⒉+y⒉=(x+y)⒉-2xy=7*7-2*10=29
（2）(x-y)⒉=x的平方-2xy+y的平方=x的平方+y的平方-2xy=29-2*10=9

Answer 2

x+y=7
(x+y)^2=49
x^2+2xy+y^2=49
x^2+y^2=49-20=29

(x-y)⒉=x^2-2xy+y^2=29-20=9

Answer 3

X=5,Y=2;X=2,Y=5.
(1)X^2+Y^2=25+4=29
(2)(X-Y)^2=9

Answer 4

x=2,y=5
(1) = 4+25 = 29
(2) = 3*3 = 9