SOLUTION: The first three terms in the binomial expansion of (1+ kx)n are 1− 21x +189x2.
Find the value of n and the value of k.
Please show all the steps etc... I know the answe
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Question 367543: The first three terms in the binomial expansion of (1+ kx)n are 1− 21x +189x2.
Find the value of n and the value of k.
Please show all the steps etc... I know the answer, but I don't understand the solution at all... thanks
Answer by robertb(5830) (Show Source): You can put this solution on YOUR website!
The first three terms of the expression are . Hence
nk = -21, and
, after equating coefficients.
The foregoing equation is the same as . Hence
by substitution,
, or ,
or 21k = -63, or k = -3. From nk = -21, n = 7.
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