GMAT Practice Question: If x=-\frac{5}{8} and y=-\frac{1}{2}, what is the value of the expression -2 x-y^{2} ?
Question
If x=-\frac{5}{8} and y=-\frac{1}{2}, what is the value of the expression -2 x-y^{2} ?
- -\frac{3}{2}
- -1
- 1
- \frac{3}{2}
- \frac{7}{4}
Topics: function variable substitution, fractions, calculations, exponents
Solution
Step 1
We first note the values of x and y as given.
x = -\frac{5}{8} y = -\frac{1}{2}
Step 2
We substitute these values into the expression.
-2x - y^{2} = -2 \times (-\frac{5}{8}) - (-\frac{1}{2})^{2}
Step 3
We simplify the product in the first term and reduce the fraction.
-2 \times (-\frac{5}{8}) = \frac{-2 \times -5}{8} = \frac{\cancel{2} \times 5}{\cancel{2} \times 4} = \frac{5}{4}
Step 4
We simplify the square of the fraction in the second term.
(-\frac{1}{2})^{2} = \frac{(-1)^{2}}{2^{2}} = \frac{1}{4}
Step 5
We subtract the simplified terms using a common denominator.
\frac{5}{4} - \frac{1}{4} = \frac{4}{4} = 1
Answer
1
