f(x) =x
Step-by-step explanation:
Given are three functions of x
We have to find the function whose graph is a straight line
We know that a straight line has constant slope throughout its domain
Let us check with this
I function
![f(x) =x](/tpl/images/0212/0203/a5125.png)
Differentiate to find the slope
Slope =1 = constant
Hence this is a straight line
2 function
![f(x) = x^ 2\\f'(x) =2x](/tpl/images/0212/0203/7fac4.png)
Thus slope depends on the value of x and not a constant. Â This cannot be a straight line
3 function
![f(x) =|x|\\i.e. f(x) = -x, x](/tpl/images/0212/0203/d8c1c.png)
This function has slope 1 for positive x and -1 for negative x
Since not constant cannot be a straight line
So answer is option A