Răspunsuri

2014-04-27T16:03:10+03:00

x²-y²=(x+y)(x-y)⇒20=5(x-y)⇒x-y=20/5⇒x-y=4

(x-y)²=4²=16

2014-04-27T16:04:37+03:00
 x²-y² =20<=>(x-y)(x+y)=20 (1)
 x+y =5 (2)
(2)->(1)=> (x-y)*5=20
(x-y)=4|
² (ridicam toata ecuati la ²)

(x-y)
²=4²=>(x-y)²=16