Question

Daca x pătrat-6x=-9, atunci x=?

Answer 1

$\displaystyle x^2-6x=-9 \\ x^2-6x+9=0 \\ a=1,b=-6,c=9 \\ \Delta=b^2-4ac=6^2-4 \cdot 1 \cdot 9=36-36=0 \\ x_1=x_2=- \frac{b}{2a} =- \frac{-6}{2 \cdot 1} =- \frac{-6}{2} =-(-3)=3 \\ S=\{3\}$