Question

已知x的平方减y的平方等于15,x+y=5,求x-y的值

Answer 1

x的平方减y的平方等于15
因式分解后 （x+y）*（x-y）=15
x+y=5
所以x-y=15/5=3

Answer 2

x-y=(x²-y²)/(x+y)=15/5=3;

Answer 3

x²-y²=(x+y)(x-y)=13因为x+y=5所以x-y=13/5

Answer 4

把x2-y2分解成(x+y)(x-y)=15.所以x-y=3

Answer 5

x^2-y^2=15=(x+y)(x-y)=5(x-y)
x-y=3