as you can see, the terms exponents, for the first term, starts at highest, 5 in this case, then every element it goes down by 1, till it gets to 0
for the second term, starts at 0, and every element it goes up by 1, till it gets to the highest
now, to get the coefficient, they way I get it, is "the product of the current coefficient and the exponent of the first term, divided by the exponent of the second term plus 1"
notice the first coefficient is always 1
so...how did we get 10 for the 3rd element? well, 5*4/2
how did we get 10 for the fourth element? well, 10*2/4
and from there, you can simplify the elements of the expansion by combining the coefficients
like for example, the 7th element of (3a+4b)⁸ will then be 1032192a²b⁶
