Vô tỉ hả giết luôn!
\(y^2+5y-20=y^2+2,5y+2,5y+6,25-26,25\)
\(=\left(y+2,5\right)^2-\left(\sqrt{26,25}\right)^2\)
\(=\left(y+2,5-\sqrt{26,25}\right)\left(y+2,5+\sqrt{26,25}\right)\)
Chúc bạn học tốt!!!
\(y^2+5y-20=y^2+5y+6,25-26,25\)
\(=\left(y+2,5\right)^2-\left(\dfrac{\sqrt{105}}{2}\right)^2=\left(y+2,5-\dfrac{\sqrt{105}}{2}\right)\left(y+2,5+\dfrac{\sqrt{105}}{2}\right)\)
\(y^2+5y-20\)
=\(y^2+5y+6,25-26,25=(y+2,5)^2-(√26,25)^2\)
=\(\left(y+2,5-\text{√26,25}\right)\left(y+2,5+\text{√26,25}\right)\)
