Question: The remainder when the total wage bill $W(x)$ is divided by $(x-500)$ is $160000$ and when it is divided by $(x+400)$ the remainder is $70000$, where $x$ is the current basic fee. The committee plans to increase the basic fee from $20000$ to $25000$ if the remainder when $W(x)$ is divided by $x^2-100x-200000$ is less than $2650000$ basing on the current basic fee. Committee is not sure if the wage increase should be approved.
1. **State the problem:**
We are given the remainders when $W(x)$ is divided by $(x-500)$ and $(x+400)$, and we want to find the remainder when $W(x)$ is divided by $x^2 - 100x - 200000$. Then, based on this remainder at the current basic fee $x=20000$, decide if the wage increase to $25000$ should be approved.
2. **Recall the Remainder Theorem:**
- The remainder when a polynomial $W(x)$ is divided by $(x-a)$ is $W(a)$.
- Since $x^2 - 100x - 200000 = (x-500)(x+400)$, the remainder when dividing by this quadratic is a linear polynomial $R(x) = Ax + B$.
3. **Use given remainders to find $R(x)$:**
- Given $W(500) = 160000$ (remainder when divided by $x-500$)
- Given $W(-400) = 70000$ (remainder when divided by $x+400$)
Since $R(x)$ is the remainder when dividing by $(x-500)(x+400)$, it must satisfy:
$$R(500) = W(500) = 160000$$
$$R(-400) = W(-400) = 70000$$
Let $R(x) = Ax + B$. Then:
$$A(500) + B = 160000$$
$$A(-400) + B = 70000$$
4. **Solve the system for $A$ and $B$:**
Subtract second equation from first:
$$500A + B - (-400A + B) = 160000 - 70000$$
$$500A + B - (-400A) - B = 90000$$
$$500A + 400A = 90000$$
$$900A = 90000$$
$$A = \frac{90000}{900} = 100$$
Substitute $A=100$ into first equation:
$$100 \times 500 + B = 160000$$
$$50000 + B = 160000$$
$$B = 160000 - 50000 = 110000$$
So,
$$R(x) = 100x + 110000$$
5. **Evaluate remainder at current basic fee $x=20000$:**
$$R(20000) = 100 \times 20000 + 110000 = 2000000 + 110000 = 2110000$$
6. **Compare remainder with threshold $2650000$:**
Since $2110000 < 2650000$, the remainder is less than the threshold.
7. **Conclusion:**
Based on the current basic fee, the remainder condition is satisfied, so the committee can approve the wage increase from $20000$ to $25000$.