1.

If f : R → R and g : R → R are defined by f (x) = 2x + 3 and g(x) = x2 + 7, then the values of x such that g{f (x)} = 8 are(a) 1, 2 (b) – 1, 2 (c) – 1, – 2 (d) 1, – 2

Answer»

Answer : (c) – 1, – 2 

g{f (x)}= 8 ⇒ g{2x + 3} = 8 

⇒ (2x + 3)2 + 7 = 8 

⇒ 4x2 + 12x + 9 – 1 = 0 

⇒ 4x2 + 12x + 8 = 0 

⇒ x2 + 3x + 2 = 0 

⇒ (x + 1) (x + 2) = 0 

x = – 1, – 2.



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