Question

Difficulty: MediumBinary Operations

A binary operation \star defined on the set of real numbers R\mathbb{R} is given by xy=x+yxy+1x \star y = \frac{x + y}{x - y + 1} for xy1x - y \neq -1. If 5p=35 \star p = 3, what is the value of pp?

Answer: 3.25

Answer

The value of pp is 3.253.25 (or 134\frac{13}{4}).
Applying the operation rule xy=x+yxy+1x \star y = \frac{x + y}{x - y + 1} with x=5x = 5 and y=py = p gives 5+p6p=3\frac{5 + p}{6 - p} = 3. Cross-multiplying gives 5+p=183p5 + p = 18 - 3p, which simplifies to 4p=134p = 13 or p=3.25p = 3.25.

Step-by-Step Solution

1
Substitute x=5x = 5 and y=py = p into the given binary operation definition
5+p5p+1=3\frac{5 + p}{5 - p + 1} = 3
This sets up the equation for the given condition 5p=35 \star p = 3.
2
Simplify the denominator in the algebraic fraction
5+p6p=3\frac{5 + p}{6 - p} = 3
Combining the constants 5+1=65 + 1 = 6 simplifies the denominator.
3
Multiply both sides by (6p)(6 - p) and expand
5+p=183p5 + p = 18 - 3p
Eliminating the denominator allows linear terms in pp to be collected.
4
Rearrange terms to solve for pp
4p=13    p=3.254p = 13 \implies p = 3.25
Adding 3p3p to both sides and subtracting 55 gives 4p=134p = 13.

Key Concept

Solving linear equations derived from non-commutative binary operations
Rate this question