Question

Solve the following quadratic equation by the formula method

$3x^2+7x-20=0$

Answer 1

$$\begin{gathered} 3x^2+7x-20=0 \\ \Rightarrow 3x^2+12x-5x-20=0 \\ \Rightarrow 3x(x+4)-5(x+4)=0 \\ \Rightarrow (x+4)(3x-5)=0 \end{gathered}$$

Either,

$$\begin{gathered} x+4=0\text{or}3x-5=0 \\ \Rightarrow x=-4\text{or}x=\frac{5}{3} \end{gathered}$$

Hence, $\mathit{x}\mathbf{}\mathbf{=}\mathbf{}\mathbf{-}\mathbf{4}\mathbf{}\text{or}\mathbf{}\mathit{x}\mathbf{}\mathbf{=}\mathbf{}\frac{\mathbf{5}}{\mathbf{3}}$ are the solution of given quadratic equation.