Q11 of 14 Page 1

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

If a quadratic equation ax2 + bx + c = 0, a ≠ 0 has equal roots then


Discriminant, D = b2 – 4ac


⇒ mx2 – 7mx + 49 = 0


Substituting values in D


we get


D = 0


⇒ 49m2 – 4m(49) = 0


⇒ m2 – 4m = 0


⇒ m(m – 4) = 0


⇒ m = 0, 4


Now, m ≠ 0 isn’t possible because in that case we will have


0 + 49 = 0, which is absurd.


Hence, m = 4.


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