9 Solve the quadratic equation \( 21 x^{2}-12 x+1=0 \)
A 0.074 or 0.645
B 0.101 or 0.470
C -0.645 or 0.074
\( D \quad-0.470 \) or 0.101

Answer

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Answer

\(x \approx 0.074 \) or \(x \approx 0.645\)

Steps

Step 1 ：\(x = \frac{-b \pm \sqrt{b^{2} - 4ac}}{2a}\)

Step 2 ：\(x = \frac{12 \pm \sqrt{(-12)^{2} - 4(21)(1)}}{2(21)}\)

Step 3 ：\(x = \frac{12 \pm \sqrt{144 - 84}}{42}\)

Step 4 ：\(x = \frac{12 \pm \sqrt{60}}{42}\)

Step 5 ：\(x \approx 0.074 \) or \(x \approx 0.645\)