Answer: C) 13
===========================================================
Step-by-step explanation:
Refer to the graph below. The blue region is the set of (x,y) points that make every inequality mentioned to be true.
This region is a rectangle such that
and
So x spans from 0 to 4, while y spans from -1 to 5. We include both endpoints for each x and y interval.
---------
The corner points of the blue shaded region are:
- A = (0, -1)
- B = (0, 5)
- C = (4, 5)
- D = (4, -1)
which will be plugged into the equation P = 2x+y to see which produces the largest output.
Let's try point A
P = 2x+y
P = 2(0)-1
P = -1
Repeat for point B
P = 2x+y
P = 2(0)+5
P = 5
Then point C
P = 2x+y
P = 2(4)+5
P = 13
Finally point D
P = 2x+y
P = 2(4)-1
P = 7
We see that 13 is the largest P output value and it occurs when (x,y) = (4,5)
This is why choice C) 13 is the final answer.
----------------
Here's another way to see why choice C is the answer.
We want 2x+y to be as large as possible. Therefore, we want both x and y to be as large as possible. This happens when (x,y) = (4,5) since this corner point is the most distant from the origin (0,0) and it's located in the first quadrant.
So x is largest when x = 4 and y is largest when y = 5. This leads to 2x+y = 2(4)+5 = 13 being the largest value of P.