when the screen is placed 3 m away from the object then for real image formation on the screen by the convex lens ,what can be the max. focal length?

My rank is 29k, General, should I opt for any state college cse branch or some Nits in which in which I am getting ECE , chemical, mechanics etc....

 

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Can class 9th students study syllabus class  of 11th 

Sum of series 2[n/2] ! [n/2]!/ n! [2Co-2C2+3C2....+[-1]^n[n+1]2Cn] where n is an even positive integer. Kindly provide solution of this question and how to generalise this. How do we know that which expansion will give this?