CMI-2020-DataScience-A: 18

Question

The sum and product of the roots of the polynomial $9x^2+171x-81$ are, respectively:

• A. $-19$ and $-9$
• B. $19$ and $9$
• C. $-9$ and $19$
• D. $9$ and $-19$

Answer 1

For the quadratic equation $ax^2+bx+c=0$,

the sum of it’s root =$-\frac{b}{a}$,

product of it’s root= $\frac{c}{a}$

compair the equation $9x^2+171x-81$ with standred equation,we get:

$a=9$

$b=171$

$c=-81$

$\therefore$ sum of root=$-\frac{171}{9}=-19$

product of root= $-\frac{81}{9}=-9$

Option A is correct.

Answer 2