1.

What are the roots of the equation log10 (x2 – 6x + 45) = 2?(a) 9, –5 (b) –9, 5 (c) 11, – 5 (d) –11, 5

Answer»

(c) 11, – 5

Given, log10 (x2 – 6x + 45) = 2 ⇒ x2 – 6x + 45 = 102 = 100 

⇒ x2 – 6x – 55 = 0 ⇒ x2 – 11x + 5x – 55 = 0 

⇒ x(x – 11) + 5(x – 11) = 0 ⇒ (x + 5) (x – 11) = 0 

⇒ x = – 5 or 11.



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