Question

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Solve the compound inequality. Write the solutions in interval notation.
x + 7 ≥ 4 and 11x - 8 ≥ 3

Answer 1

Answer: [1, infinity)

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Step-by-step explanation:

Let's isolate x in the first inequality mentioned.

x + 7 ≥ 4

x + 7-7 ≥ 4-7

x ≥ -3

I subtracted 7 from both sides to undo the +7.

Now isolate x in the second inequality. We first add 8 to both sides, then divide both sides by 11.

11x - 8 ≥ 3

11x - 8+8 ≥ 3+8

11x ≥ 11

11x/11 ≥ 11/11

x ≥ 1

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The two solutions we found were

x ≥ -3 and x ≥ 1

Next, draw out a number line with closed circles at -3 and 1. Shade to the right of each closed circle endpoint as you see below.

Notice that the two inequalities overlap for x ≥ 1

In other words, if a number is -3 or larger AND 1 or larger, then the number is 1 or larger.

The two solutions intersect to form x ≥ 1

The inequality x ≥ 1 is the same as 1 ≤ x which is the same as 1 ≤ x < infinity

Then that turns into the interval notation of [1, infinity)

The square bracket includes the endpoint 1.

If needed, use the infinity symbol in place of the word "infinity".

Answer 2

[1, ∞)

Step-by-step explanation:

To solve a compound inequality, first separate it into two inequalities and solve them separately:

Solution of Inequality 1:

x + 7 ≥ 4

⇒ x ≥ 4 - 7

⇒ x ≥ -3

Solution of Inequality 2:

11x - 8 ≥ 3

⇒ 11x ≥ 3 + 8

⇒ 11x ≥ 11

⇒ x ≥ 1

As both graphs overlap for x ≥ 1, this is the solution.

Therefore, in interval notation: [1, ∞)