How do you solve -15x^2 - 10x + 40 = 0 using the quadratic formula?
1 Answer
Aug 14, 2015
Explanation:
For a general form quadratic equation
color(blue)(ax^2 + bx + c = 0)
the two possible roots of the equation take the form - this is the quadratic formula
color(blue)(x_(1,2) = (-b +- sqrt(b^2 - 4ac))/(2a)
Now, your quadratic equation looks like this
-15x^2 - 10x + 40 = 0
You can divide all the terms by
-3x^2 - 2x + 8 = 0
In your case, you have
x_(1,2) = (-(-2) +- sqrt( (-2)^2 - 4 * (-3) * 8))/(2 * (-3))
x_(1,2) = (2 +- sqrt(100))/(-6)
x_(1,2) = (2 +- 10)/(-6) = -(1 +- 5)/3 = {(x_1 = (-1 - 5)/3 = -2), (x_2 = (-1 + 5)/3 = 4/3) :}
Your quadratic equation will thus have two roots,
