MCQ
If $a{x^2} + bx + c = 0$, then $x =$
- A$\frac{{b \pm \sqrt {{b^2} - 4ac} }}{{2a}}$
- B$\frac{{ - b \pm \sqrt {{b^2} - ac} }}{{2a}}$
- ✓$\frac{{2c}}{{ - b \pm \sqrt {{b^2} - 4ac} }}$
- DNone of these
=$\frac{{2c\,( - b - \sqrt {{b^2} - 4ac} )}}{{4ac}} = \frac{{ - b - \sqrt {{b^2} - 4ac} }}{{2a}}$
Similarly $\frac{{2c}}{{ - b - \sqrt {{b^2} - 4ac} }} \times \frac{{ - b + \sqrt {{b^2} - 4ac} }}{{ - b + \sqrt {{b^2} - 4ac} }}$
=$\frac{{2c\,( - b + \sqrt {{b^2} - 4ac} )}}{{4ac}} = \,\frac{{ - b + \sqrt {{b^2} - 4ac} }}{{2a}}$
Aliter : On rationalising the given equation
$x = \frac{{ - b \pm \sqrt {{b^2} - 4ac} }}{{2a}}$, we get option $(c)$ correct.
Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.