Question : If $x=1-y$ and $x^2=2-y^2$, then what is the value of $xy$?
Option 1: $1$
Option 2: $2$
Option 3: $-\frac{1}{2}$
Option 4: $–1$
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Correct Answer: $-\frac{1}{2}$
Solution : Given: $x = 1-y$ ⇒ $x+y = 1$ Squaring both sides, we get, ⇒ $x^2+y^2+2xy=1$ Using $x^2 = 2-y^2$ ⇒ $2-y^2+y^2+2xy=1$ ⇒ $2+2xy =1$ $\therefore xy = -\frac{1}{2}$ Hence, the correct answer is $-\frac{1}{2}$.
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Question : If $xy = -6$ and $x^3+ y^3= 19$ ($x$ and $y$ are integers), then what is the value of $\frac{1}{x^{–1}}+\frac{1}{y^{–1}}$?
Option 1: –1
Option 2: –2
Option 3: 1
Option 4: 2
Question : If $x=\frac{\sqrt{5}+1}{\sqrt{5}-1}$ and $y=\frac{\sqrt{5}-1}{\sqrt{5}+1}$, then the value of $\frac{x^{2}+xy+y^{2}}{x^{2}-xy+y^{2}}$ is:
Option 1: $\frac{3}{4}$
Option 2: $\frac{4}{3}$
Option 3: $\frac{3}{5}$
Option 4: $\frac{5}{3}$
Question : If $\sin17°=\frac{x}{y}$, then the value of $(\sec17°–\sin73°)$ is:
Option 1: $\frac{y^{2}}{x\sqrt{y^{2}–x^{2}}}$
Option 2: $\frac{x^{2}}{y\sqrt{y^{2}–x^{2}}}$
Option 3: $\frac{x^{2}}{y\sqrt{x^{2}–y^{2}}}$
Option 4: $\frac{y^{2}}{x\sqrt{x^{2}–y^{2}}}$
Question : If $xy(x+y)=m$, then the value of $(x^3+y^3+3m)$ is:
Option 1: $\frac{m^3}{xy}$
Option 2: $\frac{m^3}{(x+y)^3}$
Option 3: $\frac{m^3}{x^3y^3}$
Option 4: $mx^3y^3$
Question : If $x+y+z=0$, then what is the value of $\frac{x^2}{yz}+\frac{y^2}{xz}+\frac{z^2}{xy}$?
Option 1: $0$
Option 2: $\frac{1}{3}$
Option 3: $1$
Option 4: $3$
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