516,214 views
41 votes
41 votes
Please help me with these graphs i am not sure which one should be correct in order to explain this to my son. I have attached the pictures of the graph What graph represents the system of linear inequalities?2x+y<1y≥1/2x+2

Please help me with these graphs i am not sure which one should be correct in order-example-1
User Ton Plomp
by
3.3k points

1 Answer

14 votes
14 votes

The given inequalities are

2x + y < 1

y ≥ x/2 + 2

The first step is to write both inequalities as equations. We have

2x + y = 1

y = x/2 + 2

The next step is to plot the straight line graphs for each equation. Since we are given options, we would find the x and y intercepts of each equation and select the graph that matches them.

Recall, x intercept is the value of x when y is zero

y intercept is the value of y when x is zero

For the first equation,

when x = 0, we have

2(0) + y = 1

0 + y = 1

y = 0. This means that y intercept = 0

when y = 0,

2x + 0 = 1

2x = 1

x = 1/2 = 0.5

This means that x intercept = 0.5

The line representing this equation should pass through the y axis at y = 0 and the x axis at x = 0.5

Also, the line would be dashed(not solid) because the solutions to the inequality do not include the values on the line.

For the second equation,

when x = 0, y = 0/2 + 2 = 0 + 2 = 2

when y = 0, we have

0 = x/2 + 2

x/2 = 0 - 2 = - 2

x = - 2 * 2 = - 4

The line representing this equation should pass through the y axis at y = 2 and the x axis at x = - 4

Also, the line would be a solid line because the solutions to the inequality include the values on the line.

The next step is to determine the shaded region for each inequality. Where the shaded regions overlap is the solution. The shaded regions in each option indicate the solution. We would pick points which we would test in each of the shaded regions

For the first option, let us pick a point in the shaded region. Let us pick x = - 2 and y = 2

We would plug these values in both inequalities and see if they satisfy it.

For the first,

2x + y < 1

y < 1 - 2x

Plugging in x = - 2 and y = 2, we have

2< 1 - 2(-2)

2 < 1 + 4

2 < 5

This is true

For the second,

y≥ x/2 + 2

Plugging in x = - 2 and y = 2, we have

2 ≥ -2/2 + 2

2 ≥ - 1 + 2

2 ≥ 1

This is also true

Thus, the first option is correct

User Vallo
by
3.2k points
Welcome to QAmmunity.org, where you can ask questions and receive answers from other members of our community.