Given pair of lines are x² + 4xy + y² = 0
⇒ (y/x) ² + 4 y/x + 1 = 0
⇒ y/x = -4±2√3/2 = -2±√3,
∴ The lines y = (-2 + √3) x and y = (-2 - √3) x and x - y = 4 forms an equilateral triangle
Clearly the pair of lines x² + 4xy +y² = 0 intersect at origin,
The perpendicular distance form origin to x - y = 4 is the height of the
h = 2 √ 2
∵ Area of triangle = h²/√3 = 8/√3
2560000 sequences of answers are possible.
<em><u>Explanation</u></em>
Total number of questions = 10
First 4 questions have 5 choices each and remaining (10-4)= 6 questions have 4 choices each.
So, the possible sequences of answers for first 4 questions
and the possible sequences of answers for remaining 6 questions
Thus, the total possible number of sequences of answers = (625 × 4096) = 2560000