Basic Mathematics & Logarithm
System of linear inequalities
Grade 11

Question:

<p>Solution of \(\dfrac{2x+1}{7x-1}>5\), \(\dfrac{x+7}{x-8}>2\) linear inequalities is</p>
<p>\(x\in(8,3)\)</p>
<p>\(x\in\left(\dfrac{1}{7},\dfrac{2}{11}\right)\)</p>
<p>\(1>x\geq 7\)</p>
<p>not possible</p>

Step-by-Step Solution

Key Concept: Solve each inequality separately by moving all terms to one side and finding critical points, then find the intersection of solution sets using a number line or sign analysis.
<p><strong>Step 1: Solve the first inequality</strong> $\frac{2x+1}{7x-1}>5$</p><p>$\frac{2x+1}{7x-1}-5>0$</p><p>$\frac{2x+1-5(7x-1)}{7x-1}>0$</p><p>$\frac{2x+1-35x+5}{7x-1}>0$</p><p>$\frac{-33x+6}{7x-1}>0$</p><p>$\frac{33x-6}{7x-1}<0$ (multiplying by -1)</p><p>Critical points: $x=\frac{6}{33}=\frac{2}{11}$ and $x=\frac{1}{7}$</p><p>Since $\frac{1}{7}≈0.143$ and $\frac{2}{11}≈0.182$, we have $\frac{1}{7}<\frac{2}{11}$</p><p>Sign analysis shows: $\frac{1}{7}<x<\frac{2}{11}$</p><p><strong>Step 2: Solve the second inequality</strong> $\frac{x+7}{x-8}>2$</p><p>$\frac{x+7}{x-8}-2>0$</p><p>$\frac{x+7-2(x-8)}{x-8}>0$</p><p>$\frac{x+7-2x+16}{x-8}>0$</p><p>$\frac{-x+23}{x-8}>0$</p><p>Critical points: $x=23$ and $x=8$</p><p>Sign analysis shows: $8<x<23$</p><p><strong>Step 3: Find intersection</strong></p><p>First inequality: $\frac{1}{7}<x<\frac{2}{11}$ (approximately $0.143<x<0.182$)</p><p>Second inequality: $8<x<23$</p><p>These intervals do not overlap, so the solution set is $\emptyset$ (empty set) or no solution.</p><p>∴ Answer: D</p>
Correct Answer: D

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