Q6 of 82 Page 4

Find the value of m so that the quadratic equation mx (x – 7) + 49 = 0 has two equal roots. (CBSE 2011)

Roots of an equation are given by the formula:

x = , where, D = b2 – 4ac


For equal roots, D = 0


On comparing with ax2 + bx + c = 0, we get: a = m, b = -7m, c = 49


Therefore, D = 0


49m2 – 4m(49) = 0


49m (m - 4) = 0


m = 0 or m = 4

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