Q28 of 39 Page 91

Find the values of p for which the quadratic equation:

(2p + 1)x2 – (7p + 2)x + (7p – 3) = 0 have equal roots.

(2p + 1)x2 – (7p + 2)x + (7p – 3) = 0


Let us find Discriminant of the given equation. For equal roots of a quadratic equation, Discriminant equals to zero.


Discriminant, D = b2 – 4 ac


Where, a = (2 p + 1), b = (7 p + 2) and c = (7 p – 3)


Putting these values for finding discriminant.


D = (7 p + 2)2 – 4 (2 p + 1) ( 7 p – 3)


D = 49 p2 + 28 p + 4 – (56 p2 + 4 p – 12)


Now for equal roots D = 0


49 p2 + 28 p + 4 – (56 p2 + 4 p – 12) = 0


–7 p2 + 24 p + 16 = 0


7 p2 – 24 p – 16 = 0


For finding values of “p”, apply the Quadratic formula,


We know that the solution of equation ax2 + bx + c = 0 is given by:



For our quadratic equation, a = 7, b = – 24 and c = – 16





So, p = –56/14 or p = 8/14


Thus the possible values of p are – 4 and 4/7


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