1.

If x = 1, is common root of equation ax2 + ax + 3 = 0 and x2 + x + b = 0, then ab will be:(A) 1(B) 3.5(C) 6(D) 3

Answer»

Answer is (D) 3

Putting x = 1 in equation

ax2 + ax + 3 = 0

⇒ a(1)2 + a(1) + 3 = 0

⇒ a + a + 3 = 0

⇒ 2a = – 3

⇒ a = -3/2

and putting x = 1 in equation

x2 + x + b = 0

⇒ (1)2 + (1) + b = 0

⇒ 1 + 1 + b = 0

⇒ b = -2

ab = -3/2 × -2 = 3


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