Question

Difficulty: EasyBinary Operations

A binary operation \star on the set of real numbers is defined by ab=3a+2b1a \star b = 3a + 2b - 1. What is the value of xx such that 4x=254 \star x = 25?

  1. A
    6
  2. 7Answer
  3. C
    11
  4. D
    14

Answer

The value of xx is 77.
Applying the binary operation definition ab=3a+2b1a \star b = 3a + 2b - 1 with a=4a = 4 and b=xb = x gives 3(4)+2x1=253(4) + 2x - 1 = 25. Simplifying gives 2x+11=252x + 11 = 25, leading to 2x=142x = 14 and x=7x = 7.

Step-by-Step Solution

1
Substitute a=4a = 4 and b=xb = x into the definition of the binary operation ab=3a+2b1a \star b = 3a + 2b - 1.
4x=3(4)+2x14 \star x = 3(4) + 2x - 1
Applying the given rule for the binary operation.
2
Simplify the expression on the left-hand side.
4x=12+2x1=2x+114 \star x = 12 + 2x - 1 = 2x + 11
Performing basic arithmetic multiplication and addition of constants.
3
Set the simplified expression equal to 2525 and solve for xx.
2x+11=25    2x=14    x=72x + 11 = 25 \implies 2x = 14 \implies x = 7
Subtracting 1111 from both sides and dividing by 22.

Key Concept

Evaluation of non-commutative binary operations and solving algebraic equations involving operational rules.
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