Q.

If the parabola y=ax2+bx+c has vertex at (4, 2) and a∈[1,3], then the absolute difference between the extreme values of abc is

1 3600  
2 144  
3 3456  
4 169  

Ans.

(3)

-b2a=4⇒b=-8a

16a+4b+c=2    

c=16a+2

As a∈[1,3]⇒c∈[18,50]