Q. Which is equal to 1991?Choices:(A) 19−9(B) −19−91(C) −199(D) 199
Understand Expression: Understand the given expression 1991. The expression 1991 represents the reciprocal of 19 raised to the power of 9.
Apply Negative Exponent Rule: Apply the negative exponent rule.The negative exponent rule states that a−m=am1. Therefore, to express 1991 with a negative exponent, we can write it as 19−9.
Match with Choices: Match the expression with the given choices.Comparing the expression 19−9 with the given choices, we find that it matches choice (A) 19−9.