In the expansion of (2+3x)^n the coefficients of x^3 and x^4 are in the raio 8:15. Find n.

ratios are in 8:15, therefore,

BUT OMG the answer is 8!!!!!!!!!!!!!!!!

WHY!! what's wrong with my working out.

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- October 5th 2009, 05:20 PMdifferentiateFinding n given the ratio of nCr to another ratio
In the expansion of (2+3x)^n the coefficients of x^3 and x^4 are in the raio 8:15. Find n.

ratios are in 8:15, therefore,

BUT OMG the answer is 8!!!!!!!!!!!!!!!!

WHY!! what's wrong with my working out. - October 5th 2009, 07:03 PMSoroban
Hello, differentiate!

Quote:

In the expansion of , the coefficients of and are in the raio 8:15.

.

. . . . . These are wrong

. .

. .

Then: .

. . . . . .

. . . . . .