Solved on Feb 29, 2024

Find the values of xx where 3x219x14>03x^2 - 19x - 14 > 0.

STEP 1

Assumptions
1. The function is given by k(x)=3x219x14k(x) = 3x^2 - 19x - 14.
2. We need to find all values of xx for which k(x)>0k(x) > 0.

STEP 2

To find the values of xx for which k(x)>0k(x) > 0, we need to determine the roots of the quadratic equation k(x)=0k(x) = 0. We can do this by using the quadratic formula:
x=b±b24ac2ax = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}
where a=3a = 3, b=19b = -19, and c=14c = -14.

STEP 3

First, calculate the discriminant (b24ac)(b^2 - 4ac) of the quadratic equation.
Δ=b24ac\Delta = b^2 - 4ac
Δ=(19)24(3)(14)\Delta = (-19)^2 - 4(3)(-14)

STEP 4

Calculate the value of the discriminant.
Δ=361+168\Delta = 361 + 168 Δ=529\Delta = 529

STEP 5

Since the discriminant Δ>0\Delta > 0, there are two distinct real roots. Now, use the quadratic formula to find the roots.
x=(19)±52923x = \frac{-(-19) \pm \sqrt{529}}{2 \cdot 3}

STEP 6

Simplify the expression inside the quadratic formula.
x=19±236x = \frac{19 \pm 23}{6}

STEP 7

Calculate the two values of xx.
x1=19+236=426=7x_1 = \frac{19 + 23}{6} = \frac{42}{6} = 7 x2=19236=46=23x_2 = \frac{19 - 23}{6} = \frac{-4}{6} = -\frac{2}{3}

STEP 8

The roots of the equation k(x)=0k(x) = 0 are x=7x = 7 and x=23x = -\frac{2}{3}. The quadratic function k(x)k(x) will be positive between the roots and negative outside the roots since the leading coefficient a=3a = 3 is positive.

STEP 9

The values of xx for which k(x)>0k(x) > 0 are in the intervals (,23)(-\infty, -\frac{2}{3}) and (7,)(7, \infty).
The values of xx for which k(x)>0k(x) > 0 are all xx such that x<23x < -\frac{2}{3} or x>7x > 7.

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