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Question: If circles x<sup>2</sup> + y<sup>2</sup> – 3x + ly – 5 = 0 and 4x<sup>2</sup> + 4y<sup>2</sup> – 12x...

If circles x2 + y2 – 3x + ly – 5 = 0 and 4x2 + 4y2 – 12x + y – 9 = 0 are concentric then l equals

A

14\frac{1}{4}

B

14- \frac{1}{4}

C

18\frac{1}{8}

D

18- \frac{1}{8}

Answer

14\frac{1}{4}

Explanation

Solution

x2 + y2 – 3x + ly – 5 = 0 ̃ centre º (3/2, –l/2)

x2 + y2 – 3x + 14\frac{1}{4}y – 94\frac{9}{4} = 0 ̃ centre º (32,18)\left( \frac{3}{2}, - \frac{1}{8} \right)

\ l = 14\frac{1}{4}