A binary operation on the set of rational numbe... - JAMB Mathematics 2006 Question
A binary operation * on the set of rational numbers is defined as \(x \times y = \frac{x^2 - y^2}{2xy}find -5 \times 3\)
A
\(\frac{-8}{15}\)
B
\(\frac{8}{15}\)
C
\(\frac{17}{15}\)
D
\(\frac{-17}{15}\)
correct option: a
\(x \times y = \frac{x^2 - y^2}{2xy}find -5 \times 3\\
=\frac{(x+y)(x-y)}{2xy}\\
=\frac{(-5+3)(-5-3)}{2(-5\times3)}\\
=\frac{-2 \times -8}{2(-5\times3)}\\
=\frac{-8}{15}\)
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