Question : If $\frac{x+1}{x-1}=\frac{a}{b}$ and $\frac{1-y}{1+y}=\frac{b}{a}$, then the value of $\frac{x-y}{1+xy}$ is:
Option 1: $\frac{2ab}{a^{2}-b^{2}}$
Option 2: $\frac{a^{2}-b^{2}}{2ab}$
Option 3: $\frac{a^{2}+b^{2}}{2ab}$
Option 4: $\frac{a^{2}-b^{2}}{ab}$
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Correct Answer: $\frac{2ab}{a^{2}-b^{2}}$
Solution : $\frac{x+1}{x-1}=\frac{a}{b}$ ⇒ $bx+b = ax-a$ ⇒ $x = \frac{a+b}{a-b}$ Multiplying and dividing by $(a+b)$ in RHS, we get: ⇒ $x=\frac{(a+b)^2}{a^2-b^2}$ ----------------(i) Again, $\frac{1-y}{1+y}=\frac{b}{a}$ ⇒ $a-ay = b+by$ ⇒ $y=\frac{a-b}{a+b}$ Multiplying and diving by $(a-b)$ in RHS, we get: ⇒ $y=\frac{(a-b)^2}{a^2-b^2}$----------------(ii) From (i) and (ii), $\frac{x-y}{1+xy}$ = $\frac{\frac{(a+b)^2}{a^2-b^2}-\frac{(a-b)^2}{a^2-b^2}}{1+[\frac{(a+b)^2}{a^2-b^2}×\frac{(a-b)^2}{a^2-b^2}]}$ = $\frac{\frac{(a+b)^2-(a-b)^2}{a^2-b^2}}{1+\frac{(a^2-b^2)^2}{(a^2-b^2)^2}}$ = $\frac{\frac{4ab}{a^2-b^2}}{2}$ = $\frac{2ab}{a^{2}-b^{2}}$ Hence, the correct answer is $\frac{2ab}{a^{2}-b^{2}}$.
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Question : If $X$ is 20% less than $Y$, then find the values of$\frac{Y–X}{Y}$ and $\frac{X}{X–Y}$.
Option 1: $\frac{1}{5}$ and $-4$
Option 2: $5$ and $-\frac{1}{4}$
Option 3: $\frac{2}{5}$ and $-\frac{5}{2}$
Option 4: $\frac{3}{5}$ and $-\frac{5}{3}$
Question : If $\sin (x - y) = \frac{1}2$ and $\cos (x + y) = \frac{1}2$, then what is the value of $\sin x \cos x + 2\sin^2x + cos^3x \sec x$?
Option 1: $2$
Option 2: $\sqrt{2}+1$
Option 3: $1$
Option 4: $\frac{3}{4}$
Question : If $x\cos \theta -y\sin \theta =\sqrt{x^{2}+y^{2}}$ and $\frac{\cos ^2{\theta }}{a^{2}}+\frac{\sin ^{2}\theta}{b^{2}}=\frac{1}{x^{2}+y^{2}},$ then the correct relation is:
Option 1: $\frac{x^{2}}{b^{2}}-\frac{y^{2}}{a^{2}}=1$
Option 2: $\frac{x^{2}}{a^{2}}+\frac{y^{2}}{b^{2}}=1$
Option 3: $\frac{x^{2}}{b^{2}}+\frac{y^{2}}{a^{2}}=1$
Option 4: $\frac{x^{2}}{a^{2}}-\frac{y^{2}}{b^{2}}=1$
Question : If $x^2+y^2=427$ and $xy=202$, then find the value of $\frac{x+y}{x-y}$.
Option 1: $\sqrt{\frac{835}{23}}$
Option 2: $\sqrt{\frac{830}{29}}$
Option 3: $\sqrt{\frac{831}{23}}$
Option 4: $\sqrt{\frac{830}{23}}$
Question : What is the value of $\frac{4x^2+9y^2+12xy}{144}$?
Option 1: $(\frac{x}{3} + \frac{y}{4})^2$
Option 2: $(\frac{x}{3} + y)^2$
Option 3: $(\frac{x}{4} + \frac{y}{6})^2$
Option 4: $(\frac{x}{6} + \frac{y}{4})^2$
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