Official Solution:If \(x = 10^{10}\), \(\frac{x^2 + 2x + 7}{3x^2 - 10x + 200}\) is closest to:A. \(\frac{1}{6}\)
B. \(\frac{1}{3}\)
C. \(\frac{2}{5}\)
D. \(\frac{1}{2}\)
E. \(\frac{2}{3}\)
Reduce by \(x^2\) to get \(\frac{x^2 + 2x + 7}{3x^2 - 10x + 200} = \frac{1 + \frac{2}{x} + \frac{7}{x^2} }{3 - \frac{10}{x} + \frac{200}{x^2} }\).
For large \(x\), such as \(10^{10}\), terms like \(\frac{2}{x}\), \(\frac{7}{x^2}\), \(\frac{10}{x}\), and \(\frac{200}{x^2}\) become significantly small and approach 0. As a result, the fraction approximates \(\frac{1}{3}\).
Alternative Explanation Substitute: \(x = 10^{10}\):
\(\frac{x^2 + 2x + 7}{3x^2 - 10x + 200}=\)
\(=\frac{10^{20} + 2*10^{10} + 7}{3*10^{20} - 10*10^{10} + 200}\).
Note that we are asked to find an
approximate value of the expression. Now, observe that \(10^{20}\) is a significantly larger number than \(2*10^{10} + 7\), which makes \(2*10^{10} + 7\) negligible in comparison. Likewise, \(3*10^{20}\) is much larger than \(-10*10^{10} + 200\), rendering \(-10*10^{10} + 200\) also negligible.
Therefore, \(\frac{10^{20} + 2*10^{10} + 7}{3*10^{20} - 10*10^{10} + 200} \approx \frac{10^{20} }{3*10^{20} }=\frac{1}{3}\).
Answer: B