Solve for X: Balancing Inequalities in 8x < 3x + 9 and 5x + 4 < 0

Compound Inequalities with Solution Intervals

which value of X satisfies:

8x<3x+9 8x< 3x+9

but does not exist in:

5x+4<0 5x+4<0

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1

Understand the problem

which value of X satisfies:

8x<3x+9 8x< 3x+9

but does not exist in:

5x+4<0 5x+4<0

2

Step-by-step solution

To solve this problem, we will address each inequality separately and examine the conditions:

Step 1: Solving the First Inequality

The first inequality is 8x<3x+9 8x < 3x + 9 .

  • Subtract 3x 3x from both sides to isolate terms with x x :

8x3x<9 8x - 3x < 9

5x<9 5x < 9

  • Divide both sides by 5 to solve for x x :

x<95 x < \frac{9}{5}

Thus, the solution to the first inequality is x<1.8 x < 1.8 .

Step 2: Solving the Second Inequality

The second inequality is 5x+4<0 5x + 4 < 0 .

  • Subtract 4 from both sides:

5x<4 5x < -4

  • Divide both sides by 5:

x<45 x < -\frac{4}{5}

Thus, x<0.8 x < -0.8 .

Step 3: Analyzing the Combined Conditions

  • We need to find the values of x x that satisfy x<1.8 x < 1.8 (from Step 1) but do not satisfy x<0.8 x < -0.8 (from Step 2).
  • This indicates x x should be greater than or equal to 0.8-0.8 and still less than 1.8 1.8 .

Therefore, the solution is 0.8x<1.8 -0.8 \leq x < 1.8 .

Thus, the value of x x satisfies the desired condition, which corresponds to choice 3 in the options provided.

Therefore, the solution to the problem is 0.8x<1.8 -0.8 \leq x < 1.8 .

3

Final Answer

0.8x<1.8 -0.8 ≤ x < 1.8

Key Points to Remember

Essential concepts to master this topic
  • Rule: Solve each inequality separately before combining conditions
  • Technique: For 8x < 3x + 9, subtract 3x: 5x < 9, so x < 1.8
  • Check: Test x = 0: satisfies x < 1.8 but not x < -0.8 ✓

Common Mistakes

Avoid these frequent errors
  • Combining inequalities before solving each one
    Don't try to solve both inequalities together in one step = confusion and wrong intervals! This mixes up the conditions and leads to incorrect solution sets. Always solve each inequality completely first, then analyze what values satisfy one condition but not the other.

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

What does 'does not exist in' mean for inequalities?

+

It means we want values that don't satisfy the second inequality. If 5x+4<0 5x + 4 < 0 gives x<0.8 x < -0.8 , then 'not existing' means x0.8 x ≥ -0.8 .

Why is the answer -0.8 ≤ x < 1.8 instead of -0.8 < x < 1.8?

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Because we need values that do not satisfy x<0.8 x < -0.8 . The boundary value x = -0.8 doesn't satisfy the strict inequality, so we include it with ≤.

How do I know which inequality symbol to use at each boundary?

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Check each boundary carefully! For x = 1.8: since 8(1.8)=3(1.8)+9 8(1.8) = 3(1.8) + 9 , it's not less than, so use <. For x = -0.8: it doesn't satisfy the second condition, so include it with ≤.

Can I graph these inequalities to visualize the solution?

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Absolutely! Draw number lines for each inequality. The first gives you everything left of 1.8, the second gives everything left of -0.8. The answer is the region that's in the first but not in the second.

What if both inequalities had the same direction?

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Then you'd either have an intersection (values satisfying both) or a union (values satisfying either). Always read the problem carefully to see if it wants 'and', 'or', or 'but not' conditions.

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