Question

x₁² + x₂² = ?

Vi ét là:

x₁ + x₂ =7/2

x₁.x₂= 3

Answer 1

\(x_1^2+x_2^2=\left(x_1+x_2\right)^2-2x_1x_2\)

\(=\left(\dfrac{7}{2}\right)^2-2.3\)

\(=\dfrac{25}{4}\)

Answer 2

x1^2+x2^2=(x1+x2)^2-2x1x2

=49/4-2*3=49/4-6

=25/4

Answer 3

\(x_1^2+x_2^2=\left(x_1+x_2\right)^2-2x_1x_2=\left(\dfrac{7}{2}\right)^2-3.2=\dfrac{49}{4}-6=\dfrac{25}{4}\)