{"id":6471,"date":"2021-10-16T17:33:17","date_gmt":"2021-10-16T12:03:17","guid":{"rendered":"https:\/\/mathemerize.com\/?p=6471"},"modified":"2021-11-20T01:33:12","modified_gmt":"2021-11-19T20:03:12","slug":"formula-for-binomial-theorem","status":"publish","type":"post","link":"https:\/\/mathemerize.com\/formula-for-binomial-theorem\/","title":{"rendered":"Formula for Binomial Theorem"},"content":{"rendered":"
Here you will learn formula for binomial theorem of class 11 with examples.<\/p>\n
Let’s begin –<\/p>\n
If x and a are real numbers, then for all n \\(\\in\\) N.<\/p>\n
\n\\((x + a)^n\\) = \\(^{n}C_0 x^n a^0\\) + \\(^{n}C_1 x^{n – 1} a^1\\)\u00a0+ …………… + \\(^{n}C_r x^{n – r} a^r\\) + …………… + \\(^{n}C_{n – 1} x^1 a^{n – 1}\\) + \\(^{n}C_n x^0 a^n\\)<\/p>\n
i.e. \\((x + a)^n\\) = \\(\\sum_{r=0}^{n}\\) \\(^{n}C_{r} x^{n-r} a^{r}\\)<\/p>\n<\/blockquote>\n
Some Importants Result From Binomial Theorem<\/strong><\/h4>\n
(1)\u00a0<\/strong>We have.<\/p>\n
\n\\((x + a)^n\\) = \\(\\sum_{r=0}^{n}\\) \\(^{n}C_{r} x^{n-r} a^{r}\\).<\/p>\n
or, \\((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
Since r can have values from 0 to n, the total number of terms in the expansion is (n + 1).<\/p>\n
(2)<\/strong> The sum of the indices of x and a in each term is n.<\/p>\n
(3)<\/strong> Since \\(^{n}C_r\\) = \\(^{n}C_{n – r}\\)<\/p>\n
\n\\(\\implies\\) \\(^{n}C_0\\) = \\(^{n}C_n\\), \\(^{n}C_1\\) = \\(^{n}C_{n-1}\\), \\(^{n}C_2\\) = \\(^{n}C_{n – 2}\\) = …….<\/p>\n<\/blockquote>\n
So, the coefficients of terms equidistant from the beginning and end are equal. These coefficients are known as binomial coefficients.<\/p>\n
(4)<\/strong> Replacing a by -a, we get<\/p>\n
\n\\((x – a)^n\\) = \\(^{n}C_0 x^n a^0\\) – \\(^{n}C_1 x^{n – 1} a^1\\) + …………… + \\((-1)^r\\)\\(^{n}C_r x^{n – r} a^r\\) + …………… + \\((-1)^n\\)\\(^{n}C_n x^0 a^n\\)<\/p>\n
i.e.\u00a0 \\((x – a)^n\\) = \\(\\sum_{r=0}^{n}\\) \\((-1)^r\\) \\(^{n}C_{r} x^{n-r} a^{r}\\)<\/p>\n<\/blockquote>\n
Thus, the terms in the expansion of \\((x – a)^n\\) are alternatively positive and negative, the last term is positive or negative according as n is even or odd.<\/p>\n
(5)<\/strong> Putting x = 1 and a = x in the expansion of \\((x + a)^n\\), we get<\/p>\n
\n\\((1 + x)^n\\) = \\(^{n}C_0\\) + \\(^{n}C_1 x\\) + \\(^{n}C_2 x^2\\) + ……… + \\(^{n}C_r x^r\\) + \\(^{n}C_n x^n\\)<\/p>\n
i.e.\u00a0 \\((1 + x)^n\\) = \\(\\sum_{r=0}^{n}\\) \\(^{n}C_r x^r\\)<\/p>\n<\/blockquote>\n
This is the expansion of \\((1 + x)^n\\) in ascending powers of x.<\/p>\n
(6)<\/strong> Putting a = 1 in the expansion of \\((x + a)^n\\), we get.<\/p>\n
\n\\((1 + x)^n\\) = \\(^{n}C_0 x^n\\) + \\(^{n}C_1 x^{n-1}\\) + \\(^{n}C_2 x^{n-2}\\) + ……… + \\(^{n}C_r x^{n-r}\\) + \\(^{n}C_{n-1} x\\) + \\(^{n}C_n\\).<\/p>\n
i.e.\u00a0 \\((1 + x)^n\\) = \\(\\sum_{r=0}^{n}\\) \\(^{n}C_r x^{n-r}\\)<\/p>\n<\/blockquote>\n
This is the expansion of \\((1 + x)^n\\) in descending powers of x.<\/p>\n
(7)<\/strong> Putting x = 1 and a = -x in the expansion of \\((x + a)^n\\), we get<\/p>\n
\n\\((1 – x)^n\\) = \\(^{n}C_0\\) – \\(^{n}C_1 x\\) + \\(^{n}C_2 x^2\\) + ……… + \\((-1)^r\\)\\(^{n}C_r x^r\\) + \\((-1)^n\\) \\(^{n}C_n x^n\\).<\/p>\n
i.e.\u00a0 \\((1 – x)^n\\) = \\(\\sum_{r=0}^{n}\\) \\((-1)^n\\) \\(^{n}C_r x^r\\)<\/p>\n<\/blockquote>\n
(8)<\/strong> The coefficient of (r + 1)th term in the expansion of \\((1 + x)^n\\) is \\(^{n}C_r\\).<\/p>\n
(9)<\/strong> The coefficient of \\(x^r\\) in the expansion of \\((1 + x)^n\\) is \\(^{n}C_r\\).<\/p>\n
Example<\/span><\/strong> : Expand \\((x^2 + 2a)^5\\) by binomial theorem.<\/p>\n
Solution<\/span><\/strong> : Using binomial theorem, we have<\/p>\n
\\((x^2 + 2a)^5\\) = \\(^5C_0 (x^2)^5 (2a)^0\\) + \\(^5C_1 (x^2)^4 (2a)^1\\) + \\(^5C_2 (x^2)^3 (2a)^2\\) + \\(^5C_3 (x^2)^2 (2a)^3\\) + \\(^5C_4 (x^2) (2a)^4\\) + \\(^5C_5 (x^2)^0 (2a)^5\\)<\/p>\n
= \\(x^{10}\\) + 5\\((x^8)(2a)\\) + 10\\((x^6)(4a^2)\\) + 10\\((x^4)(8a^3)\\) + 5\\((x^2)(16a^4)\\) + 325\\((a^5)\\)<\/p>\n
=\u00a0 \\(x^{10}\\) + 10\\(x^{8}a\\) + 40\\(x^{6}a^2\\) + 80\\(x^{4}a^3\\) + 80\\(x^{2}a^4\\) + 32\\(a^{5}\\)<\/p>\n
\nRelated Questions<\/h3>\n
By using binomial theorem, expand \\((1 + x + x^2)^3\\).<\/a><\/p>\n
Which is larger \\((1.01)^{1000000}\\) or 10,000?<\/a><\/p>\n\n\n