Is function A linear or nonlinear
Is function B linear or nonlinear?

Function A: Linear

Function B: Nonlinear

Step-by-step explanation:

1. When looking at tables, an easy way to tell if it's linear or not is to determine if the slope is the same between different coordinates.

Try (3,5) (6,10)

y2-y1/x2-x1

10-5/6-3

5/3

Now try (6,10) (9,15)

15-10/9-6

5/3

The slopes are the same, so this function is in fact linear.

2. For graphs, linear functions form a straight line. The line in this graph is clearly curved, so it is not linear.

The correct answer is the first option which is to isolate the constant. Completing the square is done as follows:

1. Write the equation in a way that the constants are in the right side while the terms with x are on the left. 
5x2 + 15x  = 4

2. Make sure that the coefficient of the x^2 term is 1.
5(x^2 + 3x)  = 4

3. Adding a term to both sides that will complete the square in the left side. This is done by dividing the coefficient of the x term by 2 and squaring it. Note: The same amount should be added to the right side to balance the equation.
5(x^2 + 3x + 9/4)  = 4 +45/4

5(x+3/2)^2 = 61/4