Question:

Transforming to parallel axes through a point $(p, q)$, the equation $2x^2 + 3xy + 4y^2 + x + 18y + 25 = 0$ becomes $2x^2 + 3xy + 4y^2 = 1$. Then

Updated On: Feb 2, 2024
  • $p = -2, q = 3$
  • $p = 2, q = - 3$
  • $p = 3, q = - 4$
  • $p = - 4, q = 3$
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The Correct Option is B

Solution and Explanation

The correct answer is B:\(p=2,q=-3\)
Given that;
\(2x^2+3xy+4y^2+x+18y+25=0-(i)\)
\(2x^2+3xy+4y^2=1-(ii)\)
According to the question these two are the equation after transforming to parallel axis(p,q);
i.e., (p,q) satisfies both the equations;
Now;Differentiate equation (i) and ‘x’, then we get;
\(4x+3y+1=0-(iii)\)
Similarly differentiating equation (ii) w.r.t ‘y’ we get;
\(4x+8y=48-(iv)\)
So, substituting (p,q) in equation (iii) and (iv) we get;
\(\therefore 4p+3q=-1\)
\(3p+8q=-18\)
On solving the above equation we get;
\(p=2\) and \(q=-3\)
transforming
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Concepts Used:

Straight lines

A straight line is a line having the shortest distance between two points. 

A straight line can be represented as an equation in various forms,  as show in the image below:

 

The following are the many forms of the equation of the line that are presented in straight line-

1. Slope – Point Form

Assume P0(x0, y0) is a fixed point on a non-vertical line L with m as its slope. If P (x, y) is an arbitrary point on L, then the point (x, y) lies on the line with slope m through the fixed point (x0, y0) if and only if its coordinates fulfil the equation below.

y – y0 = m (x – x0)

2. Two – Point Form

Let's look at the line. L crosses between two places. P1(x1, y1) and P2(x2, y2)  are general points on L, while P (x, y) is a general point on L. As a result, the three points P1, P2, and P are collinear, and it becomes

The slope of P2P = The slope of P1P2 , i.e.

\(\frac{y-y_1}{x-x_1} = \frac{y_2-y_1}{x_2-x_1}\)

Hence, the equation becomes:

y - y1 =\( \frac{y_2-y_1}{x_2-x_1} (x-x1)\)

3. Slope-Intercept Form

Assume that a line L with slope m intersects the y-axis at a distance c from the origin, and that the distance c is referred to as the line L's y-intercept. As a result, the coordinates of the spot on the y-axis where the line intersects are (0, c). As a result, the slope of the line L is m, and it passes through a fixed point (0, c). The equation of the line L thus obtained from the slope – point form is given by

y – c =m( x - 0 )

As a result, the point (x, y) on the line with slope m and y-intercept c lies on the line, if and only if

y = m x +c