If 3rd,4th,5th,6th term in the expansion of (x+alpha)n be respectively a,b,c and d, prove that b2-ac/c2-bd=4a/3c..

Given expansion is:

Then,

Now,

Similarly,

Again, dividing (1) by (2) and (2) by (3), we get

Now subtracting 1 from both sides of  equation (4) and (5) as:

Again, on dividing (6) by (7), we get

On multiplying (5) by (8), we get

The RHS of equation (9) is 5a/3c not 4a/3c.

Please recheck it. 

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