Example

Solving 53u2=32u\frac{5}{3u-2} = \frac{3}{2u}

Solve the rational equation 53u2=32u\frac{5}{3u - 2} = \frac{3}{2u} using the five-step strategy for equations with rational expressions. This example features two distinct variable expressions in the denominators.

Step 1 — Identify restricted values. Setting each denominator equal to zero: 3u2=03u - 2 = 0 gives u=23u = \frac{2}{3}, and 2u=02u = 0 gives u=0u = 0. Record u23u \neq \frac{2}{3} and u0u \neq 0.

Step 2 — Find the LCD. The denominators (3u2)(3u - 2) and 2u2u share no common factors, so the LCD is their product: 2u(3u2)2u(3u - 2).

Step 3 — Clear the fractions. Multiply both sides by the LCD 2u(3u2)2u(3u - 2):

2u(3u2)53u2=2u(3u2)32u2u(3u - 2) \cdot \frac{5}{3u - 2} = 2u(3u - 2) \cdot \frac{3}{2u}

Cancel the matching denominator factors: on the left, (3u2)(3u - 2) cancels, leaving 2u5=10u2u \cdot 5 = 10u. On the right, 2u2u cancels, leaving (3u2)3=9u6(3u - 2) \cdot 3 = 9u - 6:

10u=9u610u = 9u - 6

Step 4 — Solve the resulting equation. Subtract 9u9u from both sides:

u=6u = -6

Step 5 — Check. The value u=6u = -6 does not equal either restricted value (00 or 23\frac{2}{3}), so it is not extraneous. Substitute into the original equation:

53(6)2=520=14\frac{5}{3(-6) - 2} = \frac{5}{-20} = -\frac{1}{4} and 32(6)=312=14\frac{3}{2(-6)} = \frac{3}{-12} = -\frac{1}{4}

Since 14=14-\frac{1}{4} = -\frac{1}{4} is true, u=6u = -6 is confirmed as the solution.

This example illustrates a rational equation where both denominators are distinct variable expressions — one a binomial (3u2)(3u - 2) and one a monomial 2u2u. The LCD is the product of both denominators, and unlike Example 8.60, the resulting equation after clearing fractions is linear rather than quadratic, yielding a single solution.

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Updated 2026-04-21

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