Solve Complex Fraction Equation: Finding A, B, C in (A/x + Bx/2) = (2x-3)²/x - C

Fraction Equations with Polynomial Expansion

Ax+Bx2=(2x3)2xc \frac{A}{x}+\frac{Bx}{2}=\frac{(2x-3)^2}{x}-c

Calculate the values of A, B, and C.

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:15 Let's find A, B, and C that make the equation true.
00:20 First, multiply by the common denominator to get rid of fractions.
00:49 Now, rearrange the equation terms neatly.
00:55 Use the multiplication formulas to expand any brackets.
01:13 Next, calculate the squares and products carefully.
01:27 Expand each bracket by multiplying with the factors.
01:37 Compare like terms to figure out A, B, and C.
01:43 Here's the solution for B.
01:49 Use the same method to find values for C and A.
01:58 Now, this is the solution for C.
02:06 And finally, here's the solution for A.
02:10 Great job! That's how we solve the problem!

Step-by-step written solution

Follow each step carefully to understand the complete solution
1

Understand the problem

Ax+Bx2=(2x3)2xc \frac{A}{x}+\frac{Bx}{2}=\frac{(2x-3)^2}{x}-c

Calculate the values of A, B, and C.

2

Step-by-step solution

To solve this problem, we'll proceed with the following steps:

  • Step 1: Expand the expression (2x3)2(2x-3)^2 on the right-hand side.
  • Step 2: Simplify the resulting expression by dividing by xx.
  • Step 3: Compare the terms on both sides of the equation to deduce the coefficients AA, BB, and CC.

Now, let us work through these steps:

Step 1: Expand the expression (2x3)2(2x-3)^2.

(2x3)2=4x212x+9 (2x - 3)^2 = 4x^2 - 12x + 9

Step 2: Substitute back into the equation and simplify by dividing by xx:

Ax+Bx2=4x212x+9xC \frac{A}{x} + \frac{Bx}{2} = \frac{4x^2 - 12x + 9}{x} - C

This simplifies to:

4x12+9xC 4x - 12 + \frac{9}{x} - C

Step 3: To find AA, BB, and CC, compare coefficients of similar terms:

  • Constant term (no xx): Equate 12-12 with C-C to get C=12C = 12 (note: should consider sign reversal).
  • Coefficient of xx: Compare B2\frac{B}{2} to 4. Giving B=8B = 8.
  • Coefficient of 1x\frac{1}{x}: Compare AA to 9, giving A=9A = 9.

Therefore, the solution to the problem is that the values are A = 9, B = 8, C = -12 \textbf{A = 9, B = 8, C = -12} .

3

Final Answer

A=9,B=8,C=12 A=9,B=8,C=-12

Key Points to Remember

Essential concepts to master this topic
  • Expansion Rule: Use (ax+b)2=a2x2+2abx+b2 (ax + b)^2 = a^2x^2 + 2abx + b^2 formula
  • Technique: Split division: 4x212x+9x=4x12+9x \frac{4x^2 - 12x + 9}{x} = 4x - 12 + \frac{9}{x}
  • Check: Compare coefficients of like terms: 1x \frac{1}{x} , x x , and constants match ✓

Common Mistakes

Avoid these frequent errors
  • Incorrectly expanding the squared binomial
    Don't expand (2x3)2 (2x - 3)^2 as 4x2+9 4x^2 + 9 by forgetting the middle term! This gives wrong coefficients. Always use the formula: (ab)2=a22ab+b2 (a - b)^2 = a^2 - 2ab + b^2 to get 4x212x+9 4x^2 - 12x + 9 .

Practice Quiz

Test your knowledge with interactive questions

Declares the given expression as a sum

\( (7b-3x)^2 \)

FAQ

Everything you need to know about this question

How do I expand (2x3)2 (2x - 3)^2 correctly?

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Use the formula (ab)2=a22ab+b2 (a - b)^2 = a^2 - 2ab + b^2 . Here, a=2x a = 2x and b=3 b = 3 , so: (2x)22(2x)(3)+32=4x212x+9 (2x)^2 - 2(2x)(3) + 3^2 = 4x^2 - 12x + 9

Why do I need to split up the fraction 4x212x+9x \frac{4x^2 - 12x + 9}{x} ?

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To compare coefficients properly! Split it as: 4x2x12xx+9x=4x12+9x \frac{4x^2}{x} - \frac{12x}{x} + \frac{9}{x} = 4x - 12 + \frac{9}{x} . This matches the form on the left side.

How do I find the value of C when it's negative?

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Look at the constant terms! On the right side we have 12C -12 - C , on the left side there's no constant term (which means 0). So: 0=12C 0 = -12 - C , giving C=12 C = -12 .

What does it mean to compare coefficients?

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Match terms with the same powers of x! Compare:

  • Terms with 1x \frac{1}{x} : A=9 A = 9
  • Terms with x x : B2=4 \frac{B}{2} = 4 , so B=8 B = 8
  • Constant terms: 0=12C 0 = -12 - C , so C=12 C = -12

How can I check if my values A = 9, B = 8, C = -12 are correct?

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Substitute back into the original equation! Left side: 9x+8x2=9x+4x \frac{9}{x} + \frac{8x}{2} = \frac{9}{x} + 4x . Right side: (2x3)2x(12)=9x+4x12+12=9x+4x \frac{(2x-3)^2}{x} - (-12) = \frac{9}{x} + 4x - 12 + 12 = \frac{9}{x} + 4x . They match!

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