1. **State the problem:**
We are given the function $f(x) = 3x^2 + 4x - k + 3$ and the condition $f(-1) = -2$. We need to find:
(a) The value of $k$.
(b) The value(s) of $t$ such that $f(t) = 38$.
2. **Find $k$ using $f(-1) = -2$:**
Substitute $x = -1$ into the function:
$$f(-1) = 3(-1)^2 + 4(-1) - k + 3 = 3(1) - 4 - k + 3 = 3 - 4 - k + 3$$
Simplify:
$$3 - 4 - k + 3 = (3 - 4 + 3) - k = 2 - k$$
Given $f(-1) = -2$, set equal:
$$2 - k = -2$$
Solve for $k$:
$$2 - k = -2$$
$$\Rightarrow \cancel{2} - k = \cancel{-2}$$
$$-k = -4$$
Multiply both sides by $-1$:
$$k = 4$$
3. **Rewrite the function with $k=4$:**
$$f(x) = 3x^2 + 4x - 4 + 3 = 3x^2 + 4x - 1$$
4. **Find $t$ such that $f(t) = 38$:**
Set the function equal to 38:
$$3t^2 + 4t - 1 = 38$$
Bring all terms to one side:
$$3t^2 + 4t - 1 - 38 = 0$$
$$3t^2 + 4t - 39 = 0$$
5. **Solve the quadratic equation:**
Use the quadratic formula:
$$t = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}$$
where $a=3$, $b=4$, $c=-39$.
Calculate the discriminant:
$$\Delta = b^2 - 4ac = 4^2 - 4(3)(-39) = 16 + 468 = 484$$
Calculate the square root:
$$\sqrt{484} = 22$$
Calculate the roots:
$$t = \frac{-4 \pm 22}{2 \times 3} = \frac{-4 \pm 22}{6}$$
Two solutions:
$$t_1 = \frac{-4 + 22}{6} = \frac{18}{6} = 3$$
$$t_2 = \frac{-4 - 22}{6} = \frac{-26}{6} = -\frac{13}{3}$$
**Final answers:**
(a) $k = 4$
(b) $t = 3$ or $t = -\frac{13}{3}$
Find K And T 3C1397
Step-by-step solutions with LaTeX - clean, fast, and student-friendly.