How do you solve this compound inequality 2x + 6\geq 12 or 2x + 6\leq - 4?

1 Answer
Dec 13, 2017

Our solution:

color(red)( x <= -5 or x >= 3)

Using Interval Notation:

color(blue)((-oo, -5] uu [3, oo)

Graph available supporting our solution.

Explanation:

We have a Compound Inequality :-

color(green)(2x + 6 >= 12 or 2x + 6 <= -4)

We will consider our compound inequality as two individual parts to start with:

color(green)(2x + 6 >= 12 . . . Inequality.1

color(green)(2x + 6 <= -4) . . . Inequality.2

We will start with . . . Inequality.2 first:

color(green)(2x + 6 <= -4) . . .Inequality.2

Add -6 to both sides of our inequality:

color(green)(2x + cancel (+6) cancel(- 6) <= -4 - 6

color(green)(rArr 2x <= -10

Divide both sides of the inequality by 2

color(green)(rArr (cancel 2x)/cancel 2 >= -10/2

color(green)(rArr x >= -5 color(red)( ... Intermediate.Answer.1)

Next we will consider . . . Inequality.1 :

color(green)(2x + 6 >= 12 . . . Inequality.1

Add -6 to both sides of our inequality:

color(green)(2x + cancel (+6) cancel(- 6) >= 12 - 6

color(green)(rArr 2x >= 6

Divide both sides of the inequality by 2

color(green)(rArr (cancel 2x)/cancel 2 >= 6/2

color(green)(rArr x >= 3 color(red)( ... Intermediate.Answer.2)

Using our intermediate answers 1 and 2 we can write our solutions as:

color(red)( x <= -5 or x >= 3)

Using Interval Notation:

color(blue)((-oo, -5] uu [3, oo)

Refer to the graph below for a better understanding:

enter image source here

I hope you find this solution useful.