Question

A salesman sold 25 items, the number of sales increased at the rate of 20 items per day. Which of the given equations represent the correct number of sales the salesman made along with its domain?

• A. $y=20x-25,\text{Domain}\le 0$
• B. $y=20x+25,\text{Domain}\ge 0$
• C. $y=20x-15,\text{Domain}\ge 0$
• D. $y=20x+15,\text{Domain}\le 0$

Answer 1

The correct option is B $y=20x+25,\text{Domain}\ge 0$

Given:

The salesman first sold 25 items.
So, initial value of sales (c) = 25

The number of sales is increasing at the rate of 20 items per day i.e., rate of change (m) = 20

$\text{We know, an equation in slope-intercept}$
$\text{form is}y=mx+c$

So, the equation for sales will $\text{be}y=20x+25$

The domain is the set of all the input values for the function.

Here, x can take all positive real values starting from zero.

$\text{∴ The domain will be}x\ge 0,\text{and}$
$\text{positive real numbers including 0}.$