Use the given transformation to evaluate the integral.
double integral R (x − 8y) dA,
where R is the triangular region with vertices (0, 0), (7, 1), and (1, 7).
x = 7u + v, y = u + 7v
double integral R (x − 8y) dA,
where R is the triangular region with vertices (0, 0), (7, 1), and (1, 7).
x = 7u + v, y = u + 7v