00:01
Hello students, to find the coefficient of a specific term in a binomial expansion, we can use the binomial theorem formula.
00:08
The formula states that for the binomial expansion of a plus b to the power n, the coefficient of xm yn is given by coefficient equal to nm into am into b to the power n, where nm is the binomial coefficient.
00:32
So this is equal to n factorial by m factorial n minus m factorial.
00:39
Now let's apply to this given cases.
00:41
So for the first one to find x to the power 5, y square in the expansion of 3x minus 2y to the power 7, here a equal to 3x, b equal to minus 2y, n equal to 7, m equal to 5.
01:01
So n minus m equal to 2.
01:06
So binomial coefficient 7, 5 equal to 7 factorial by 5 factorial by 2 factorial.
01:15
This is equal to 6 into 7 by 2, 3 into 7 equal to 21.
01:21
Now coefficient of 21 into 3x to the power 3 into minus 2y to the power 2.
01:34
This is equal to 21 into 9.
01:39
This is 5, 3x to the power 5, 2y to the power 2.
01:46
So 21 into 243 into x to the power 5 into 4 into y square.
02:00
This is equal to 21 into 972 x to the power 5 y square.
02:06
So 20 ,412 x to the power 5 y square.
02:10
So we got the coefficient...