Bunuel
If \(x > 1\) and \(\frac{a}{b} = 1 - \frac{1}{x}\), then \(\frac{b}{a} =\)
A. x
B. x - 1
C. \(\frac{x - 1}{x}\)
D. \(\frac{x}{x - 1}\)
E. \(\frac{1}{x} - 1\)
We are asked for the reciprocal of
\(\frac{a}{b}\).
We can take the reciprocal of RHS only if RHS expression is a single number or a single fraction.
(If fractions are added or subtracted on RHS, find the sum or difference. Then flip the resultant fraction.)
\(\frac{a}{b} = 1 - \frac{1}{x}\)
\(\frac{a}{b} = (\frac{1}{1}*\frac{x}{x}) - (\frac{1}{x}*\frac{x}{x})\)
\(\frac{a}{b} = \frac{x}{x}-\frac{1}{x}\)
\(\frac{a}{b} = \frac{(x-1)}{x}\)
\(\frac{b}{a} = \frac{x}{(x-1)}\)Answer D
Or use \(\frac{1}{a}-\frac{1}{b}=\frac{b-a}{ab}\). From original fractions, use numbers in the denominator. Subtract first number from second number (b-a) for the new numerator. Multiply the numbers (ab) for the new denominator.