Given the function $f(x) = \frac{ax^2 + bx + c}{x - 2}$, we need to determine the values of $a$, $b$, and $c$ such that the curve (C) representing $f(x)$ satisfies the following conditions: * (C) passes through the point A(0, 5). * The tangent to (C) at point A is parallel to the x-axis. * The tangent to (C) at the point B with x-coordinate 1 has a slope of -3.

AlgebraCalculusDerivativesTangentsFunctionsFinding Coefficients
2025/4/3

1. Problem Description

Given the function f(x)=ax2+bx+cx2f(x) = \frac{ax^2 + bx + c}{x - 2}, we need to determine the values of aa, bb, and cc such that the curve (C) representing f(x)f(x) satisfies the following conditions:
* (C) passes through the point A(0, 5).
* The tangent to (C) at point A is parallel to the x-axis.
* The tangent to (C) at the point B with x-coordinate 1 has a slope of -
3.

2. Solution Steps

* Condition 1: (C) passes through A(0, 5)
This means f(0)=5f(0) = 5. Substituting x=0x = 0 into the function:
f(0)=a(0)2+b(0)+c02=c2f(0) = \frac{a(0)^2 + b(0) + c}{0 - 2} = \frac{c}{-2}
So, c2=5\frac{c}{-2} = 5, which implies c=10c = -10.
* Condition 2: The tangent at A(0, 5) is parallel to the x-axis.
This means f(0)=0f'(0) = 0. Let's find the derivative f(x)f'(x):
f(x)=(2ax+b)(x2)(ax2+bx+c)(1)(x2)2f'(x) = \frac{(2ax + b)(x - 2) - (ax^2 + bx + c)(1)}{(x - 2)^2}
f(x)=2ax24ax+bx2bax2bxc(x2)2f'(x) = \frac{2ax^2 - 4ax + bx - 2b - ax^2 - bx - c}{(x - 2)^2}
f(x)=ax24ax2bc(x2)2f'(x) = \frac{ax^2 - 4ax - 2b - c}{(x - 2)^2}
Now, we set f(0)=0f'(0) = 0:
f(0)=a(0)24a(0)2bc(02)2=2bc4=0f'(0) = \frac{a(0)^2 - 4a(0) - 2b - c}{(0 - 2)^2} = \frac{-2b - c}{4} = 0
This implies 2bc=0-2b - c = 0. Since c=10c = -10, we have 2b(10)=0-2b - (-10) = 0, which gives 2b+10=0-2b + 10 = 0, so b=5b = 5.
* Condition 3: The tangent at B(1, f(1)) has a slope of -

3. This means $f'(1) = -3$. We have $f'(x) = \frac{ax^2 - 4ax - 2b - c}{(x - 2)^2}$. Substituting $x = 1$, $b = 5$, and $c = -10$:

f(1)=a(1)24a(1)2(5)(10)(12)2=a4a10+101=3af'(1) = \frac{a(1)^2 - 4a(1) - 2(5) - (-10)}{(1 - 2)^2} = \frac{a - 4a - 10 + 10}{1} = -3a
So, 3a=3-3a = -3, which implies a=1a = 1.
Therefore, a=1a = 1, b=5b = 5, and c=10c = -10.

3. Final Answer

a=1a = 1, b=5b = 5, c=10c = -10