Rational Expressions
P(x)/Q(x) — polynomial over polynomial. Simplify by canceling common factors. Domain: exclude roots of Q. Holes: canceled factors. Vertical asymptotes: remaining roots of denominator.
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Hole at x=a if (x−a) cancels in numerator and denominator. Vertical asymptote at x=a if (x−a) remains in denominator after simplifying. LCD = product of distinct factors from all denominators.
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Why: Rational expressions model rates, concentrations, and transfer functions. Simplifying reveals structure. Domain restrictions prevent division by zero. Holes vs asymptotes: canceled vs uncanceled roots.
How: Simplify: factor numerator and denominator, cancel common factors. Add/subtract: find LCD, convert, combine. Multiply: multiply across. Divide: multiply by reciprocal. Domain: set denominator ≠ 0.
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📐 Examples — Click to Load
Expression 1: P(x) / Q(x)
Coefficient Comparison
Canceled vs Remaining Factors
📐 Calculation Steps
For educational and informational purposes only. Verify with a qualified professional.
🧮 Fascinating Math Facts
(x²−1)/(x−1)=x+1 for x≠1. Hole at x=1.
— Hole Example
1/x has vertical asymptote at x=0 — domain x≠0.
— Asymptote
📋 Domain Restrictions
A rational expression p(x)/q(x) is undefined when q(x)=0. Always exclude these values from the domain. Example: (x²-4)/(x-2) has domain x≠2 because x-2=0 when x=2.
- • Holes: Values that make both numerator and denominator zero. After canceling, the factor is gone but the value is still excluded.
- • Vertical asymptotes: Values that make only the denominator zero (after cancellation). The graph approaches ±∞.
- • Simplification: Factor both numerator and denominator, cancel common factors. The simplified form equals the original for all x in the domain.
🔄 Operations with Fractions
📖 Simplification Rules
Step 1: Factor the numerator and denominator completely.
Step 2: Identify common factors.
Step 3: Cancel common factors. The canceled values are holes in the graph.
Step 4: Remaining denominator roots are vertical asymptotes.
Example: (x²-4)/(x-2) = (x-2)(x+2)/(x-2) = x+2 for x≠2. Hole at x=2.
📊 Holes vs Asymptotes
| Type | Condition | Graph behavior |
|---|---|---|
| Hole | Num and den both zero | Removable discontinuity |
| VA | Only den zero (after cancel) | Graph → ±∞ |
📐 Worked Examples
(x²-4)/(x-2)
Factor: x²-4 = (x-2)(x+2). Cancel (x-2): result = x+2 for x≠2. Hole at x=2.
(x²+5x+6)/(x²+3x+2)
Num = (x+2)(x+3), Den = (x+1)(x+2). Cancel (x+2): (x+3)/(x+1) for x≠-1,-2. Hole at x=-2, VA at x=-1.
Real-world: Work rate
If A does 1/x job/hr and B does 1/(x+1) job/hr, combined rate = 1/x + 1/(x+1) = (2x+1)/(x(x+1)).
⚠️ Input format: Enter coefficients as comma-separated, highest degree first. E.g. "1,0,-4" for x²-4, "1,-2" for x-2.
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