Question

What should be added to $(x+2{)}^3=2x(x^2-1)$ to make it a quadratic equation.

Answer 1

$\Rightarrow$ A quadratic equation is an equation of the second degree.

$\Rightarrow$ $(x+2{)}^3=2x(x^2-1)$

$\Rightarrow$ $x^3+3\times x^2\times 2+3\times (2{)}^2\times x+(2{)}^3=2x^3-2x$

$\Rightarrow$ $x^3+6x^2+12x+8-2x^3+2x=0$

$\Rightarrow$ $-x^3+6x^2+14x+8=0$

To make above equation quadratic equation we have add $x^3$ on left side of the equation,

$\Rightarrow$ $-x^3+6x^2+14x+8+x^3=0$

$\therefore$ $6x^2+14x+8=0$