Question

Which of the following is a constant?

• A. 7x - 6x - 2x + 6 - 4
• B. $\frac{21x}{7x}$
• C. 7x - 5x + 2
• D. 12x -5 + 16x + 5

Answer 1

The correct option is B $\frac{21x}{7x}$

A constant is a number that is fixed and known, unlike a variable whose value changes.

a) 7x - 6x - 2x + 6 - 4 can be simplified to -x + 2, an expression with variables.

b) $\frac{21x}{7x}=3$: A constant
Note that this is valid only when $x\ne 0$.

c) 7x - 5x + 2 can be simplified to 2x + 2, an expression with variables.

d) 12x -5 + 16x + 5 can be simplified to 28x, an expression with variables.