Question

Use the quadratic formula to find the solutions for y = 3x^3 + 8x - 1

Answer 1

Answer:

Solving the equation using quadratic formula we get $\mathbf{x=0.119\:or\:x=-2.785}$

Step-by-step explanation:

We need to use the quadratic formula to find the solutions for

$y = 3x^2 + 8x - 1$

(Note: quadratic formula is used when x^2 is in the equation. So considering 3x^2 instead of 3x^3)

The quadratic formula is: $x=\frac{-b\pm\sqrt{b^2-4ac}}{2a}$

From the given equation $y = 3x^3 + 8x - 1$ we have a =3, b=8 and c =-1

Putting values in the formula and finding solutions:

$x=\frac{-b\pm\sqrt{b^2-4ac}}{2a}\\x=\frac{-8\pm\sqrt{(8)^2-4(3)(-1)}}{2(3)}\\x=\frac{-8\pm\sqrt{64+12}}{6}\\x=\frac{-8\pm\sqrt{76}}{6}\\x=\frac{-8\pm8.71}{6}\\x=\frac{-8+8.71}{6}\:or\:x=\frac{-8-8.71}{6}\\x=0.119\:or\:x=-2.785$

So, Solving the equation using quadratic formula we get $\mathbf{x=0.119\:or\:x=-2.785}$