The reciprocal of x is which expression?

The reciprocal of x is which expression?

• A. x
• B. 1/x
• C. ln x
• D. e^x

Answer: (B)

A reciprocal is the value that multiplies by a number to give 1. For a nonzero x, the partner that does this is 1/x, because x × (1/x) = 1. So the reciprocal of x is 1/x (undefined if x = 0). For example, if x = 5, the reciprocal is 1/5, and 5 × 1/5 = 1. The other expressions aren’t reciprocals: x would not yield 1 when multiplied by itself, and ln x and e^x are a logarithm and an exponential function, respectively, not factors that multiply to 1.

A reciprocal is the value that multiplies by a number to give 1. For a nonzero x, the partner that does this is 1/x, because x × (1/x) = 1. So the reciprocal of x is 1/x (undefined if x = 0). For example, if x = 5, the reciprocal is 1/5, and 5 × 1/5 = 1. The other expressions aren’t reciprocals: x would not yield 1 when multiplied by itself, and ln x and e^x are a logarithm and an exponential function, respectively, not factors that multiply to 1.