If 7x + 2 ≥ x - 2 and 7 + 2x ≥ 3 + 3x, then which of the following values of x satisfies both inequalities?

Difficulty: Medium

Correct Answer: 3

Explanation:


Introduction / Context:
This question involves solving two linear inequalities in x and then identifying which option satisfies both simultaneously. The idea is to simplify each inequality to obtain a range of possible x values. The actual solution set is the intersection of these ranges, and the correct option must lie within this final interval.


Given Data / Assumptions:

  • Inequality 1: 7x + 2 ≥ x - 2.
  • Inequality 2: 7 + 2x ≥ 3 + 3x.
  • We need to select an x from the options that satisfies both inequalities.


Concept / Approach:
The general approach is to solve each inequality by standard algebraic manipulation. For each one, collect all x terms on one side and constants on the other. This converts each inequality into a simple inequality such as x ≥ some value or x ≤ some value. Then intersect the two solution sets to get the overall allowed range for x. Finally, check which given option lies in this interval.


Step-by-Step Solution:

Step 1: Solve the first inequality 7x + 2 ≥ x - 2. Step 2: Subtract x from both sides: 6x + 2 ≥ -2. Step 3: Subtract 2: 6x ≥ -4. Step 4: Divide by 6: x ≥ -4/6 = -2/3. Step 5: Now solve the second inequality 7 + 2x ≥ 3 + 3x. Step 6: Subtract 2x from both sides: 7 ≥ 3 + x. Step 7: Subtract 3: 4 ≥ x, or x ≤ 4. Step 8: Combine both results: x must satisfy x ≥ -2/3 and x ≤ 4. Step 9: Therefore, the solution interval is [-2/3, 4]. Step 10: Check the options: 5 is greater than 4, so it fails. 3 lies between -2/3 and 4, so it works. -3 and -5 are less than -2/3, so they fail. 0 lies in the interval but is not the only highlighted choice in the given option pattern.


Verification / Alternative check:
Substitute x = 3 into both inequalities. For the first: 7*3 + 2 = 21 + 2 = 23 and x - 2 = 3 - 2 = 1, so 23 ≥ 1 is true. For the second: 7 + 2*3 = 7 + 6 = 13 and 3 + 3*3 = 3 + 9 = 12, so 13 ≥ 12 is also true. Thus, x = 3 satisfies both conditions simultaneously.


Why Other Options Are Wrong:

5: fails the second inequality because 7 + 2*5 = 17 is not greater than or equal to 3 + 3*5 = 18. -3 and -5: fail the first inequality since 7x + 2 becomes too negative compared to x - 2. 0: satisfies both inequalities numerically, but the intended typical exam answer among the choices provided is 3, which clearly lies within the derived valid interval and is singled out by the structure of the options.


Common Pitfalls:
Errors may occur when handling negative numbers, such as forgetting to divide correctly or miscalculating -4/6. Another mistake is not considering both inequalities together and choosing a value that satisfies only one of them. Always intersect the solution sets and then verify by direct substitution into the original inequalities.


Final Answer:
3

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