6.1.2 Exam: Semester 2 Exam Question 40 of 40 What is the solution to \( \sqrt{7 x-4}=2 \sqrt{x} \) ? A. \( -\frac{4}{3} \) B. \( -\frac{4}{5} \) C. \( \frac{4}{5} \) D. \( \frac{4}{3} \)
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The Deep Dive
To solve the equation \( \sqrt{7x - 4} = 2\sqrt{x} \), we can start by squaring both sides to eliminate the square roots. This gives us: \[ 7x - 4 = 4x \] Next, we'll isolate \( x \) by moving the \( 4x \) to the left side: \[ 7x - 4x = 4 \] This simplifies to: \[ 3x = 4 \] Dividing both sides by 3 gives us: \[ x = \frac{4}{3} \] We have to check if this solution is valid by substituting back into the original equation. When we substitute \( x = \frac{4}{3} \): Left side: \[ \sqrt{7\left(\frac{4}{3}\right) - 4} = \sqrt{\frac{28}{3} - 4} = \sqrt{\frac{28}{3} - \frac{12}{3}} = \sqrt{\frac{16}{3}} \] Right side: \[ 2\sqrt{\frac{4}{3}} = 2 \cdot \frac{2}{\sqrt{3}} = \frac{4}{\sqrt{3}} = \frac{4 \sqrt{3}}{3} \] After rationalizing the left side, we find they equate. Thus, the solution \( x = \frac{4}{3} \) is valid. Therefore, the answer is D. \( \frac{4}{3} \).
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