Binomial Theorem

Question

If the first 3 terms of the expansion of are , find the value of x and n

Solution

Recall the binomial expansion formula



Next we need to simplify



Going back to the question,


We can then form 2 equations involving n and x

Equation 1


Equation 2

Comments

  1. Alternatively, from Eqn (2):

    (nx)^2 - nx * x = 120.

    Also, from Eqn (1),
    nx = -12, (nx)^2 = 144,
    144 - (-12)x = 120
    12x = -24
    x = -2

    This method will avoid denominator..

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  2. One just has to be good at the basic mathematical operations, like multiplication, addition and subtraction to understand Vedic maths. Believe us, Vedic maths is this easy.
    supremedissertation

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