Number of values of a for which the equation ( a2 - 5a + 4) x2 + ( a2 - 1) x + ( a2 - 8a + 7) = 0 possesses more than two roots, is
If a quadratic equation has more than two roots, it is an identity.
For the given equation to be an identity, all the three coefficients should be zero.
a2 - 5a + 4 = 0, a2 - 1 = 0, a2 - 8a + 7 = 0
a = 1 or 4, a = 1 or - 1, a = 7 or 1
All the three will be zero when a = 1 or 1 is a common root.
⇒ Only at one value of a the given equation can be considered as an identity.