1.

Suppose f(x) is such a quadrant expression that it is positive for all real x. If g(x) = f(x) + f’(x) + f’’(x), then for any real x. Then for any real x. a. g(x) < 0 b. g(x) > 0 c. g(x) = 0 d. g(x) ≥ 0

Answer»

Correct option b. g(x) > 0

Explanation:

Let f(x) = ax2 + bx + c, a > 0, b2 < 4ac

(∵  f(x) > 0)

Now, g(x) = ax2 + bx + c + 2ax + b + 2a

= ax2 + (b + 2a)x + 2a + b + c

Now, (b + 2a)2 - 4a(2a + b + c)

= b2 + 4ab + 4a2 - 8a2 - 4ab - 4ac

= b2 - 4ac - 8a2 < 0 ⇒ g(x) > 0



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