Question

for the expression 21 - 21t to have a negative value, what must be true about the value of t? choose the correct answer. a. the value of t has to be 0. b. the value of t has to be less than 1. c. the value of t has to be greater than 1. d. the value of t has to be negative.

Explanation:

Step1: Set up the inequality

We want \(21 - 21t<0\).

Step2: Subtract 21 from both sides

Subtract 21 from each side: \(21 - 21t-21<0 - 21\), which simplifies to \(- 21t<-21\).

Step3: Divide both sides by -21 (and reverse inequality)

Divide both sides by -21. When dividing an inequality by a negative number, the inequality sign reverses. So \(\frac{-21t}{-21}>\frac{-21}{-21}\), which simplifies to \(t > 1\).

Answer:

C. The value of t has to be greater than 1.