Rule

x² - y² =(x+y)(x-y)

Galician ?

Dado que x e y numeros reais, tais que x - y= 89,8 & x^2 – y^2 = 8,98, obtenha o valor numérico de x+y.?

Please post in English:

x and y real numbers, such that

x - y = 89.8 and,

x^2 – y^2 = 8.98,

obtain the numerical value of x + y.

x + y = (x^2 – y^2)/(x – y) = 1/10 or 0.1