Question : $P(4,2)$ and $R(–2,0)$ are vertices of a rhombus $PQRS$. What is the equation of diagonal $QS$?
Option 1: $x–3y=–2$
Option 2: $3x+y=4$
Option 3: $3x+y=–4$
Option 4: $x–3y=2$
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Correct Answer: $3x+y=4$
Solution : $QS$ perpendicularly bisects the diagonal joining $P(4,2)$ and $R(–2,0)$ at $O$, thus $O$ is the mid-point of $PR$ and $QS$. Co-ordinates of point $O$ = $(\frac{x_1+x_2}{2},\frac{y_1+y_2}{2})$ = $(\frac{4–2}{2},\frac{2+0}{2})=(1,1)$ The slope of the straight line $PR$ = $\frac{y_2–y_1}{x_2–x_1}=\frac{0–2}{–2–4}$ = $\frac{–2}{–6}=\frac{1}{3}$ We know that $m_1m_2=–1$ $(\because PR\perp QS)$ Therefore, slope of $QS$ = $–\frac{1}{\frac{1}{3}}=–3$ Equation of the straight line $QS$ passing through the point (1, 1) ⇒ $y–1=–3(x–1)$ ⇒ $y–1=–3x+3$ ⇒ $3x+y=4$ Hence, the correct answer is $3x+y=4$.
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Question : What is the equation of the line whose y-intercept is $-\frac{3}{4}$ and making an angle of $45^{\circ}$ with the positive x-axis?
Option 1: $4x–4y=3$
Option 2: $4x-4y=–3$
Option 3: $3x–3y=4$
Option 4: $3x–3y=–4$
Question : For the triangle $PQR$, find the equation of altitude $PS$, if the co-ordinates of $P, Q, R$ are (1, 2), (2, –1), and (0, 5), respectively.
Option 1: $x–3y=–7$
Option 2: $x+3y=–5$
Option 3: $x–3y=–5$
Option 4: $x+3y=–7$
Question : Simplify the given expression $\frac{(x^3-y^3)(x+y)}{x^2+x y+y^2}$.
Option 1: $x - y$
Option 2: $x^2-y^2$
Option 3: $x + y$
Option 4: $x^2+y^2$
Question : Simplify the given expression. $\frac{x^3+y^3+z^3-3 x y z}{(x-y)^2+(y-z)^2+(z-x)^2}$
Option 1: $\frac{1}{3}(x+y+z)$
Option 2: $(x+y+z)$
Option 3: $\frac{1}{4}(x+y+z)$
Option 4: $\frac{1}{2}(x+y+z)$
Question : The equation $\cos ^{2}\theta=\frac{(x+y)^{2}}{4xy}$ is only possible when,
Option 1: $x=-y$
Option 2: $x>y$
Option 3: $x=y$
Option 4: $x<y$
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