Question

How would you do number 12 and 15?

Answer 1

Answer:

$x_1=x_2=-\dfrac{2}{3}$

Step-by-step explanation:

For the quadratic equation $ax^2+bx+c=0$ the discriminant is defined as

$D=b^2-4ac$

and the quadratic formula for the roots gives us two roots:

$x_1=\dfrac{-b-\sqrt{D}}{2a}$

and

$x_2=\dfrac{-b+\sqrt{D}}{2a}$

For the equation $9x^2 +12x+4=0$ use quadratic formula to find roots:

$D=12^2-4\cdot 9\cdot 4=144-144=0$

So,

$x_1=x_2=\dfrac{-12\pm \sqrt{0}}{2\cdot 9}=-\dfrac{12}{18}=-\dfrac{2}{3}$