Using the binomial theorem to find coefficients in binomials. About
(a) What is the coefficient of x3y4 in (-3x + 4y)7?
(b) What is the coefficient of x2y7 in (5x - y)9?
(c) What is the coefficient of x5y3 in (3x - 4y)8?
(d) What is the coefficient of x6y1 in (-2x - 5y)7?