Solve the Inequality: 0 < 8a + 4 ≤ -a + 9

Compound Inequalities with Algebraic Variables

Find a a a so that:

0<8a+4a+9 0 < 8a+4 ≤ -a+9

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1

Understand the problem

Find a a a so that:

0<8a+4a+9 0 < 8a+4 ≤ -a+9

2

Step-by-step solution

To solve this problem, we'll break it down into manageable steps:

The problem asks us to find a a satisfying two conditions simultaneously: 0<8a+4 0 < 8a + 4 and 8a+4a+9 8a + 4 \leq -a + 9 .

  • Step 1: Solve the first inequality.
  • The inequality 0<8a+4 0 < 8a + 4 can be simplified by subtracting 4 from both sides:

    4<8a -4 < 8a

    Next, divide each side by 8 to isolate a a :

    12<a -\frac{1}{2} < a
  • Step 2: Solve the second inequality.
  • The inequality 8a+4a+9 8a + 4 \leq -a + 9 can be simplified. Begin by adding a a to both sides to gather all a a -terms on one side:

    9a+49 9a + 4 \leq 9

    Subtract 4 from both sides:

    9a5 9a \leq 5

    Finally, divide each side by 9 to solve for a a :

    a59 a \leq \frac{5}{9}
  • Step 3: Combine the results of these inequalities.
  • We now combine the results from step 1 and step 2:

    The condition from step 1 is 12<a -\frac{1}{2} < a .

    The condition from step 2 is a59 a \leq \frac{5}{9} .

    Together, these conditions provide the range:

    12<a59 -\frac{1}{2} < a \leq \frac{5}{9}

The solution set is 12<a59 -\frac{1}{2} < a \leq \frac{5}{9} .

Therefore, the correct answer choice is: 12<a59 -\frac{1}{2} < a \leq \frac{5}{9} .

3

Final Answer

12<a59 -\frac{1}{2} < a ≤ \frac{5}{9}

Key Points to Remember

Essential concepts to master this topic
  • Rule: Split compound inequalities into two separate inequality statements
  • Technique: Solve 0 < 8a + 4 gives -1/2 < a
  • Check: Test boundary values in original compound inequality ✓

Common Mistakes

Avoid these frequent errors
  • Solving the compound inequality as one step
    Don't try to solve 0 < 8a + 4 ≤ -a + 9 all at once = confusion and wrong answers! This creates algebraic chaos because you're mixing different operations. Always split into separate inequalities: solve 0 < 8a + 4 AND 8a + 4 ≤ -a + 9, then combine results.

Practice Quiz

Test your knowledge with interactive questions

Solve the following inequality:

\( 3x+4 \leq 10 \)

FAQ

Everything you need to know about this question

Why do I need to split the compound inequality into two parts?

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A compound inequality like 0<8a+4a+9 0 < 8a + 4 ≤ -a + 9 actually represents two conditions that must both be true. Splitting helps you solve each part clearly without mixing up the algebra.

How do I know which inequality symbol to use when combining?

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Look at your results: 12<a -\frac{1}{2} < a AND a59 a ≤ \frac{5}{9} . The variable a must satisfy both conditions, so combine them as 12<a59 -\frac{1}{2} < a ≤ \frac{5}{9} .

What if there's no solution that satisfies both inequalities?

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Sometimes the two conditions contradict each other (like a > 5 AND a < 2). When this happens, there's no solution because no number can satisfy both conditions simultaneously.

Can I test my answer by picking a number in the range?

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Yes! Pick any number between 12 -\frac{1}{2} and 59 \frac{5}{9} , like a = 0. Substitute into the original: 0<8(0)+40+9 0 < 8(0) + 4 ≤ -0 + 9 becomes 0<49 0 < 4 ≤ 9 , which is true!

Why is one side strict inequality (<) and the other includes equality (≤)?

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This comes directly from the original problem! The left side uses strict inequality (0 <), while the right side allows equality (≤ -a + 9). Always preserve the original inequality symbols in your final answer.

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