Question

Which ordered pairs is the solution to this set of linear inequalities?

y < 2x +2 and y ≥ -x -1
a.(-1,0)
b(0,3)
c(2,0)
d(-1,-4)

Answer 1

c (2,0)

Explanation:

One way to solve this system of inequalities is to graph the inequalities and see which ordered pair lies in the shaded region that is common to both inequalities

See the graph and each of the ordered pairs. Only (2, 0) lies entirely within the shaded region

(-1, 0) lies on the intersection of the two lines so it will satisfy the >= inequality but not the < inequality

Answer (2, 0)

However if you cannot use graphing then a brute force method must be used to see which ordered pair satisfies both inequalities

a. (-1, 0)
Check y < 2x + 2 ?
=> 0 < 2(-1) + 2 ?
=> 0 < -2 + 2
0 < 0 ? False
Eliminate option a

b. (0, 3)
y < 2x + 2?
=> 3 < 2(0) + 2?
3 < 2? False
Eliminate option b

c. (2, 0)
y < 2x + 2?
=> 0 < 2(2) + 2 ?
=> 0 < 4 + 2
=> 0 < 6 True

Move to the second inequality
y ≥ -x - 1?
0 ≥ -2 - 1
0 ≥ -3 True

So option c is the correct choice

While it is not necessary to check option d, let's do it anyway
d. (-1, -4)
y < 2x + 2 ?
-4 < 2(-1) + 2 ?
-4 < -2 + 2 ?
-4 < 0 ? True

Move to the second inequality
y > -x - 1 ?
-4 > -(-1) - 1
-4 > -2? False
Option d is eliminated

Correct answer: (2, 0) which is option c