Question

Solve the equation $3y^2+8y+5=0$ by using formula method

Answer 1

$3y^2+8y+5=0$
This equation comparing with $a{y}^2+by+c=0$, we get
$a=3,b=8,c=5$
$\therefore y=\frac{-b\pm \sqrt{b^2-4ac}}{2a}$
$\Rightarrow y=\frac{-8\pm \sqrt{64-4\times 3\times 5}}{2\times 3}$
$\Rightarrow y=\frac{-8\pm \sqrt{64-60}}{6}$
$\Rightarrow y=\frac{-8\pm 2}{6}$
Taking ${}^{\prime }{+}^{\prime }$ sign, we get
$thereforey=\frac{-8+2}{6}=\frac{-6}{6}=-1$
Taking ${}^{\prime }{-}^{\prime }$ sign, we get
$\therefore y=\frac{-8-2}{6}$
$=\frac{-10}{6}$
$=\frac{-5}{3}$
$\therefore y=-1$
or $y=-\frac{5}{3}$