{"id":8274,"date":"2021-11-20T01:17:06","date_gmt":"2021-11-19T19:47:06","guid":{"rendered":"https:\/\/mathemerize.com\/?p=8274"},"modified":"2021-11-20T01:26:01","modified_gmt":"2021-11-19T19:56:01","slug":"find-the-middle-term-in-the-expansion-of-3x-x3over-67","status":"publish","type":"post","link":"https:\/\/mathemerize.com\/find-the-middle-term-in-the-expansion-of-3x-x3over-67\/","title":{"rendered":"Find the middle term in the expansion of \\((3x – {x^3\\over 6})^7\\)."},"content":{"rendered":"
The given expression is \\((3x – {x^3\\over 6})^7\\).<\/p>\n
Here n = 7, which is an odd number.<\/p>\n
By using middle terms in binomial expansion formula<\/a>,<\/p>\n So, \\(({7 + 1\\over 2}\\)) th and \\(({7 + 1\\over 2} + 1)\\) th i.e.\u00a0 4th and 5th terms are two middle terms.<\/p>\n Now, \\(T_{4}\\) = \\(T_{3 + 1}\\) = \\(^{7}C_{3}\\) \\((3x)^{7 – 3}\\) \\((-{x^3\\over 6})^{3}\\)<\/p>\n \\(\\implies\\) \\(T_{4}\\) = \\((-1)^3\\) \\(^{7}C_{3}\\) \\((3x)^{4}\\) \\(({x^3\\over 6})^{3}\\)<\/p>\n \\(\\implies\\) \\(T_{4}\\) = -35 \\(\\times\\) 81 \\(x^4\\) \\(\\times\\) \\(x^9\\over 216\\) = -\\(105x^{13}\\over 8\\)<\/p>\n and,\u00a0 \\(T_{5}\\) = \\(T_{5 + 1}\\) = \\(^{7}C_{4}\\) \\((3x)^{7 – 4}\\) \\((-{x^3\\over 6})^{4}\\)<\/p>\n \\(\\implies\\) \\(T_{5}\\) = \\(^{7}C_{4}\\) \\((3x)^{3}\\) \\(({x^3\\over 6})^{4}\\)<\/p>\n \\(\\implies\\) \\(T_{5}\\)= 35 \\(\\times\\) 27 \\(x^3\\) \\(\\times\\) \\(x^{12}\\over 1296\\) = \\(35x^{15}\\over 48\\)<\/p>\n Hence, the middle terms are -\\(105x^{13}\\over 8\\) and \\(35x^{15}\\over 48\\).<\/p>\n Find the middle term in the expansion of \\(({2\\over 3}x^2 \u2013 {3\\over 2x})^{20}\\).<\/a><\/p>\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 Which is larger \\((1.01)^{1000000}\\) or 10,000?<\/a><\/p>\n
\nSimilar Questions<\/h3>\n