Question

cho x + y = 1; x - y = 3. Tính x\(^2\) - y\(^{^{ }2}\)

Answer 1

\(x^2-y^2=\left(x+y\right)\left(x-y\right)\)

Mà \(x+y=1;x-y=3\)

\(\Rightarrow x^2-y^2=1.3=3\)

Vậy \(x^2-y^2=3\)

Answer 2

Vì x+y=1;x-y =3 \(\Rightarrow\)x=2

y = -1

Thay x=2;y=-1 ta có : \(2^2-\left(-1\right)^2=4-1=3\)

Vậy x^2 -y^2 = 3