How do you find the roots, real and imaginary, of y=2x^2 + 13x + 6+4(x -1)^2 using the quadratic formula?

1 Answer
Dec 29, 2015

x = (-5 + sqrt(-215))/12 or x = (-5 - sqrt(-215))/12

Explanation:

First expand and simplify to ensure just one term for each power of x.
y = 2x^2 +13x +6 +4(x^2 -2x + 1)
y = 2x^2 +13x + 6 + 4x^2 -8x +4
y=6x^2 +5x +10
Then use x = (-b +- sqrt(b^2 - 4ac))/(2a)
x = (-5 +- sqrt( 5^2 - 4*6*10))/(2*6)
x = (-5 +-sqrt(25 - 240))/12
x = (-5 +- sqrt(-215))/12
There are only imaginary roots to this equation, meaning that in graphical terms the graph never intersects the x axis.