QuestionAugust 25, 2025

Solve the following inequality algebraically. -6x^2+15geqslant x+8 Answer Attemptiout of 2 square

Solve the following inequality algebraically. -6x^2+15geqslant x+8 Answer Attemptiout of 2 square
Solve the following inequality algebraically.
-6x^2+15geqslant x+8
Answer Attemptiout of 2
square

Solution
3.9(218 votes)

Answer

x \in \left[-\frac{7}{6}, 1\right] Explanation 1. Rearrange the inequality Move all terms to one side: -6x^2 - x + 15 - 8 \geqslant 0 simplifies to -6x^2 - x + 7 \geqslant 0. 2. Solve the quadratic equation Use the quadratic formula x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} for -6x^2 - x + 7 = 0. Here, a = -6, b = -1, c = 7. Calculate discriminant: b^2 - 4ac = (-1)^2 - 4(-6)(7) = 1 + 168 = 169. Roots are x = \frac{-(-1) \pm \sqrt{169}}{2(-6)} = \frac{1 \pm 13}{-12}. Solutions: x = \frac{14}{-12} = -\frac{7}{6} and x = \frac{-12}{-12} = 1. 3. Test intervals Test intervals (-\infty, -\frac{7}{6}), (-\frac{7}{6}, 1), (1, \infty) in -6x^2 - x + 7 \geqslant 0. Choose test points like x = -2, x = 0, x = 2. For x = -2: -6(-2)^2 - (-2) + 7 = -24 + 2 + 7 = -15 0 (True). For x = 2: -6(2)^2 - 2 + 7 = -24 - 2 + 7 = -19 < 0 (False). 4. Determine solution set Inequality holds for x \in [-\frac{7}{6}, 1].

Explanation

1. Rearrange the inequality<br /> Move all terms to one side: $-6x^2 - x + 15 - 8 \geqslant 0$ simplifies to $-6x^2 - x + 7 \geqslant 0$.<br />2. Solve the quadratic equation<br /> Use the quadratic formula $x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}$ for $-6x^2 - x + 7 = 0$. Here, $a = -6$, $b = -1$, $c = 7$.<br /> Calculate discriminant: $b^2 - 4ac = (-1)^2 - 4(-6)(7) = 1 + 168 = 169$.<br /> Roots are $x = \frac{-(-1) \pm \sqrt{169}}{2(-6)} = \frac{1 \pm 13}{-12}$.<br /> Solutions: $x = \frac{14}{-12} = -\frac{7}{6}$ and $x = \frac{-12}{-12} = 1$.<br />3. Test intervals<br /> Test intervals $(-\infty, -\frac{7}{6})$, $(-\frac{7}{6}, 1)$, $(1, \infty)$ in $-6x^2 - x + 7 \geqslant 0$.<br /> Choose test points like $x = -2$, $x = 0$, $x = 2$.<br /> For $x = -2$: $-6(-2)^2 - (-2) + 7 = -24 + 2 + 7 = -15 < 0$ (False).<br /> For $x = 0$: $-6(0)^2 - 0 + 7 = 7 > 0$ (True).<br /> For $x = 2$: $-6(2)^2 - 2 + 7 = -24 - 2 + 7 = -19 < 0$ (False).<br />4. Determine solution set<br /> Inequality holds for $x \in [-\frac{7}{6}, 1]$.
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