: Find the equation of the circle passing through (4,1),(6,5) and having the centre on the line
4x + y-16=0.
Answers
Answer:
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Let the equation of the equation of the required circle be (x - h)² + (y - k)² = r²
Since the circle passes through points (4, 1) and (6, 5).
=> (4 - h)² + (1 - k)² = r²______(i).
=> (6 - h)² + (5 - k)² = r²______(ii).
Since the centre (h, k) of the circle lies on line 4x + y = 16 _____(iii).
From equation (i). and (ii), we obtain
=> (4 - h)² + (1 - k)² = (6 - h)² + (5 - k)²
=> 16 - 8h + h² + 1 - 2k + k² = 36 - 12k + k² + 25 - 10k + k²
=> 16 - 8h + 1 - 2k = 36 - 12k + 25 - 10k
=> 4h + 8k = 44
=> h + 2k = 11 ______(iv).
On solving equations (iii) and (iv), we obtain
On solving equations (iii) and (iv), we obtainh = 4 and k = 4.
On substitution the values of h and k in equation (i), we obtain.
=> (4 - 3)² + (1 - 4)² = r²
=> (1)² + (-3)² = r²
=> 1 + 9 = r²
=> 10 = r²
=> r = √10
So, the equation of the circle.
=> (x - 3)² + (y - 4)² = (√10)²
=> x² - 6x + 9 + y - 8y + 16 = 10
=> x² + y² - 6x - 8y + 15 = 0
Hence, the equation of the required circle is
x² + y² - 6x - 8y + 15 = 0.