{"id":6473,"date":"2021-10-16T17:33:02","date_gmt":"2021-10-16T12:03:02","guid":{"rendered":"https:\/\/mathemerize.com\/?p=6473"},"modified":"2021-11-20T01:34:26","modified_gmt":"2021-11-19T20:04:26","slug":"general-term-in-binomial-expansion","status":"publish","type":"post","link":"https:\/\/mathemerize.com\/general-term-in-binomial-expansion\/","title":{"rendered":"General Term in Binomial Expansion"},"content":{"rendered":"
Here you will learn formula to find the general term in binomial expansion with examples.<\/p>\n
Let’s begin –<\/p>\n
We have,<\/p>\n
\n\\((x + a)^n\\) = \\(^{n}C_0 x^n a^0\\) + \\(^{n}C_1 x^{n – 1} a^1\\) + …………… + \\(^{n}C_r x^{n – r} a^r\\) + …………… + \\(^{n}C_n x^0 a^n\\)<\/p>\n<\/blockquote>\n
We find that : The first term = \\(^{n}C_0 x^n a^0\\)<\/p>\n
The second term = \\(^{n}C_1 x^{n – 1} a^1\\)<\/p>\n
The third term = \\(^{n}C_2 x^{n – 2} a^2\\)<\/p>\n
The fourth term = \\(^{n}C_3 x^{n – 3} a^3\\),\u00a0 and so on.<\/p>\n
We thus observe that the suffix of C in any term is one less than the number of terms, the index of x is n minus the suffix of C and the index of a is the same as the suffix of C.<\/p>\n
Hence, the (r + 1)th term is given by \\(^{n}C_r x^{n – r} a^r\\)<\/p>\n
Thus, if \\(T_{r + 1}\\) denotes the (r + 1)th term, then<\/p>\n
General Term :<\/strong><\/h4>\n
\n\\(T_{r + 1}\\) = \\(^{n}C_r x^{n – r} a^r\\)<\/p>\n<\/blockquote>\n
This is called the general term<\/strong>, because by giving different values to r we can determine all terms of the expansion.<\/p>\n
In the binomial expansion of \\((x – a)^n\\), the general term is given by<\/p>\n
\n\\(T_{r + 1}\\) = \\((-1)^r\\)\\(^{n}C_r x^{n – r} a^r\\)<\/p>\n<\/blockquote>\n
In the binomial expansion of \\((1 + x)^n\\), we have<\/p>\n
\n\\(T_{r + 1}\\) = \\(^nC_r x^r\\)<\/p>\n<\/blockquote>\n
In the binomial expansion of \\((1 – x)^n\\), we have<\/p>\n
\n\\(T_{r + 1}\\) = \\((-1)^r\\)\\(^nC_r x^r\\)<\/p>\n<\/blockquote>\n
Nth term from the End :<\/strong><\/h4>\n
\nIn the binomial expansion of \\((x + a)^n\\), the rth term from the end is ((n + 1) – r + 1) = (n – r + 2)th term form the beginning.<\/p>\n<\/blockquote>\n
Example<\/span><\/strong> : Write the general term in the expansion of \\((x^2 – y)^6\\).<\/p>\n
Solution<\/span><\/strong> : We have, \\((x^2 – y)^6\\) = \\(|(x^2 + (-y)|^6\\)<\/p>\n
The general term in the expansion of the above binomial is given by\u00a0<\/p>\n
\\(T_{r + 1}\\) = \\(^{n}C_r x^{n – r} a^r\\)<\/p>\n
\\(\\implies\\) \\(T_{r + 1}\\) = \\(^{6}C_r (x^2)^{6 – r} (-y)^r\\)<\/p>\n
\\(\\implies\\) \\(T_{r + 1}\\) = \\((-1)^r\\)\\(^{6}C_r x^{12 – 2r} y^r\\)<\/p>\n
\nRelated Questions<\/h3>\n
Find the 9th term in the expansion of \\(({x\\over a} \u2013 {3a\\over x^2})^{12}\\).<\/a><\/p>\n
Find the 10th term in the binomial expansion of \\((2x^2 + {1\\over x})^{12}\\).<\/a><\/p>\n\n\n