In the quadratic equation 2 x ax b 0 a and b can take any value from the set 1 2 3 4 How many pairs ...........

Quantitative Aptitude (CDS) Quadratic Equations

In the quadratic equation 2 x + ax + b = 0, a and b can take any value from the set {1, 2, 3, 4}. How many pairs of values of a and b are possible in order that the quadratic equation has real roots?

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Explanation:

As we know that for real roots of quadratic equation,
Discriminant $\geq$ 0
=> a²−4b ≥ 0
=> b²≥4b ……….. (i)
The pairs which follows the condition will be
(2,1),(3,1),(3,2),(4,1),(4,2),(4,3),(4,4)
Hence total number of pairs =7
Hence option (2)