If 4x^2 + Ax + 9 = 0 , have equal roots, then find the value of A.

Madhya Pradesh Police Exam Model Paper 10

Question : 41 of 100

Marks: +1, -0

4x^2 + Ax + 9 = 0

, have equal roots, then find the value of A.

Solution:

Given:

4x^2 + Ax + 9 = 0

have equal roots.
Concept:
If equation

ax^2 + bx + c

has equal roots, the discriminant (d) should be equal to zero.

d = (b)^2 – 4 × a × c = 0

Calculation:

d = (b)^2 – 4 × a × c = 0

⇒ (A)^2 – 4 × 4 × 9 = 0

⇒ (A)^2 – 144 = 0

⇒ A = √144

⇒ A = 12

∴ The value of A is 12

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