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NTA Abhyas JEE Main2020MathematicsStraight LinesPractice

The sum of all the values of p for which the lines x + y - 1 = 0 , p x + 4 y + 2 = 0 and 4 x + p y + 7 = 0 are concurrent is equal to

Options

A0
B- 9
C- 13
D4

Correct answer

C. - 13

Step-by-step solution

1 1 - 1 p 4 2 4 p 7 = 0 ⇒ p 2 + 9 p - 52 = 0 ⇒ p = - 13 ,   4 p = 4 is rejected as at p =   4 all 3 lines become parallel.

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