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If (2x^(2)+5)/((x+1)^(2)(x-3))=(A)/(x+1)...

If `(2x^(2)+5)/((x+1)^(2)(x-3))=(A)/(x+1)+(B)/((x+1)^(2))+(C)/(x-3)` then `A=`

A

`- (15)/(4)`

B

`15/4`

C

`9/16`

D

`- 9/16`

Text Solution

AI Generated Solution

The correct Answer is:
To solve the equation \[ \frac{2x^2 + 5}{(x+1)^2(x-3)} = \frac{A}{x+1} + \frac{B}{(x+1)^2} + \frac{C}{x-3} \] we will follow these steps: ### Step 1: Set up the equation We start with the left-hand side as it is and rewrite the right-hand side with a common denominator: \[ \frac{A}{x+1} + \frac{B}{(x+1)^2} + \frac{C}{x-3} = \frac{A(x+1)(x-3) + B(x-3) + C(x+1)^2}{(x+1)^2(x-3)} \] ### Step 2: Cancel the denominators Since the denominators are the same, we can equate the numerators: \[ 2x^2 + 5 = A(x+1)(x-3) + B(x-3) + C(x+1)^2 \] ### Step 3: Expand the right-hand side Now we will expand the right-hand side: 1. Expand \(A(x+1)(x-3)\): \[ A(x^2 - 3x + x - 3) = A(x^2 - 2x - 3) \] 2. Expand \(B(x-3)\): \[ Bx - 3B \] 3. Expand \(C(x+1)^2\): \[ C(x^2 + 2x + 1) \] Combining these, we have: \[ 2x^2 + 5 = Ax^2 - 2Ax - 3A + Bx - 3B + Cx^2 + 2Cx + C \] ### Step 4: Combine like terms Now, we will combine the terms on the right-hand side: \[ ( A + C )x^2 + (-2A + B + 2C)x + (-3A - 3B + C) \] ### Step 5: Equate coefficients Now we can equate coefficients from both sides: 1. Coefficient of \(x^2\): \[ A + C = 2 \quad \text{(1)} \] 2. Coefficient of \(x\): \[ -2A + B + 2C = 0 \quad \text{(2)} \] 3. Constant term: \[ -3A - 3B + C = 5 \quad \text{(3)} \] ### Step 6: Solve for \(C\) To find \(C\), we can substitute \(x = 3\) into the original equation: \[ 2(3)^2 + 5 = A(3+1)(3-3) + B(3-3) + C(3+1)^2 \] This simplifies to: \[ 18 + 5 = C(4^2) \implies 23 = 16C \implies C = \frac{23}{16} \] ### Step 7: Substitute \(C\) back into equation (1) Substituting \(C\) into equation (1): \[ A + \frac{23}{16} = 2 \implies A = 2 - \frac{23}{16} \] Finding a common denominator: \[ A = \frac{32}{16} - \frac{23}{16} = \frac{9}{16} \] ### Final Answer Thus, the value of \(A\) is \[ \boxed{\frac{9}{16}} \] ---
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