Polynomial Divisibility 458Fee
1. **Problem:** Find $k$ if $f(x) = 3x^4 - 2x^3 + kx + 7$ is divisible by $x+1$.
2. **Formula:** If $x+1$ is a factor, then $f(-1) = 0$ (Factor Theorem).
3. **Calculation:**
$$f(-1) = 3(-1)^4 - 2(-1)^3 + k(-1) + 7 = 3 + 2 - k + 7 = 12 - k$$
Set equal to zero:
$$12 - k = 0 \implies k = 12$$
4. **Answer:** None of the options match $k=12$, so re-check the problem or options.
Since the problem states divisibility by $x+1$, and the calculation shows $k=12$, but options are A. -8 B. 8 C. 4 D. -4, the closest is none. Possibly a typo in options.
**Final answer:** $k=12$ (not listed).
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**Summary:** Using the Factor Theorem, substituting $x=-1$ into the polynomial and setting equal to zero gives $k=12$.