The sum of the coefficients of the expansion of (5a/3-2b/3)^10 is 1024.
The binomial theorem tells us that the sum of the coefficients of the expansion of (x+y)^n is given by 2^n. In this case, x = 5a/3 and y = -2b/3, so the sum of the coefficients is 2^10 = 1024.
Here is a proof of the binomial theorem:
(x+y)^n = nC0x^n + nC1x^(n-1)y + nC2x^(n-2)y^2 + ... + nCy^(n-1)x + y^n
The sum of the coefficients is given by
nC0 + nC1 + nC2 + ... + nCy^(n-1) + y^n
We can use Pascal's identity to simplify this expression:
nC0 + nC1 + nC2 + ... + nCy^(n-1) + y^n = (nC0 + y^n) + (nC1 + y^(n-1)) + ... + (nCn-1)
Pascal's identity tells us that nC0 + y^n = 2^n, so the sum of the coefficients is
2^n + (nC1 + y^(n-1)) + ... + (nCn-1)
This expression is always equal to 2^n. Therefore, the sum of the coefficients of the expansion of (x+y)^n is always 2^n.
In the case of (5a/3-2b/3)^10, x = 5a/3 and y = -2b/3, so the sum of the coefficients is 2^10 = 1024.