1. Problem: Solve the inequalities given.
2. Formula and rules: For quadratic inequalities of the form $ax^2 + bx + c > 0$, $\geq 0$, $< 0$, or $\leq 0$, first find the roots by solving $ax^2 + bx + c = 0$. Then analyze the sign of the quadratic in intervals determined by the roots.
3. a) Solve $x^2 - 3x + 2 > 0$:
- Find roots: $x^2 - 3x + 2 = 0$ factors as $(x-1)(x-2)=0$ so roots are $x=1$ and $x=2$.
- Since $a=1>0$, parabola opens upward.
- Inequality $>0$ means where parabola is above x-axis.
- Solution intervals: $(-\infty,1) \cup (2,\infty)$.
4. c) Solve $x^2 + 7x + 12 \geq 0$:
- Roots: $x^2 + 7x + 12 = 0$ factors as $(x+3)(x+4)=0$, roots $x=-3$, $x=-4$.
- Parabola opens upward.
- Inequality $\geq 0$ means parabola is on or above x-axis.
- Solution intervals: $(-\infty,-4] \cup [-3,\infty)$.
5. e) Solve $x^2 + 4x - 12 < 0$:
- Roots: Solve $x^2 + 4x - 12=0$.
- Use quadratic formula: $x=\frac{-4 \pm \sqrt{16 + 48}}{2} = \frac{-4 \pm 8}{2}$.
- Roots: $x=2$ and $x=-6$.
- Parabola opens upward.
- Inequality $<0$ means between roots.
- Solution interval: $(-6,2)$.
6. g) Solve $x^2 - x + 1 < 0$:
- Discriminant: $\Delta = (-1)^2 - 4(1)(1) = 1 - 4 = -3 < 0$.
- No real roots, parabola opens upward.
- Since no roots and $a>0$, parabola always positive.
- Inequality $<0$ has no solution.
7. i) Solve $m^2 + m - 20 \geq 0$:
- Roots: Solve $m^2 + m - 20=0$.
- Use quadratic formula: $m=\frac{-1 \pm \sqrt{1 + 80}}{2} = \frac{-1 \pm 9}{2}$.
- Roots: $m=4$ and $m=-5$.
- Parabola opens upward.
- Inequality $\geq 0$ means outside roots.
- Solution intervals: $(-\infty,-5] \cup [4,\infty)$.
Final answers:
- a) $x \in (-\infty,1) \cup (2,\infty)$
- c) $x \in (-\infty,-4] \cup [-3,\infty)$
- e) $x \in (-6,2)$
- g) No solution
- i) $m \in (-\infty,-5] \cup [4,\infty)$
Quadratic Inequalities 60C8F9
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