1. We start with the first problem: find for which values of $x$ the graph of $f(x)$ lies below the graph of $g(x)$.
2. For (a), the functions are $f(x) = x^2$ and $g(x) = -4x + 5$.
3. We want to find where $f(x) < g(x)$, so:
$$x^2 < -4x + 5$$
4. Rearrange the inequality to one side:
$$x^2 + 4x - 5 < 0$$
5. Factor the quadratic expression:
$$x^2 + 4x - 5 = (x + 5)(x - 1)$$
6. The inequality becomes:
$$(x + 5)(x - 1) < 0$$
7. This product is less than zero when the factors have opposite signs. So, between the roots:
$$-5 < x < 1$$
8. Therefore, the graph of $f$ lies below $g$ for $x$ in the interval $(-5, 1)$.
9. For (b), the functions are $f(x) = x^2 - 4x + 2$ and $g(x) = -2x^2 + 8x - 14$.
10. Find where $f(x) < g(x)$:
$$x^2 - 4x + 2 < -2x^2 + 8x - 14$$
11. Bring all terms to one side:
$$x^2 - 4x + 2 + 2x^2 - 8x + 14 < 0$$
12. Simplify:
$$3x^2 - 12x + 16 < 0$$
13. Divide entire inequality by 3:
$$\cancel{3}x^2 - \cancel{3}4x + \cancel{3} \frac{16}{3} < 0$$
which is
$$x^2 - 4x + \frac{16}{3} < 0$$
14. Calculate the discriminant $\Delta$ to check if the quadratic can be negative:
$$\Delta = (-4)^2 - 4 \cdot 1 \cdot \frac{16}{3} = 16 - \frac{64}{3} = \frac{48}{3} - \frac{64}{3} = -\frac{16}{3} < 0$$
15. Since $\Delta < 0$ and the leading coefficient is positive, the quadratic is always positive.
16. Therefore, $3x^2 - 12x + 16$ is never less than zero, so $f(x)$ is never less than $g(x)$.
17. Final answers:
- (a) $f(x) < g(x)$ for $x \in (-5, 1)$.
- (b) No values of $x$ satisfy $f(x) < g(x)$.
18. Graphical check: plotting both functions confirms these intervals.
Graph Inequalities F4Dee7
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