dz/dx= 3(5*x³*y²+1)² * 15x²y²= 45x²y² * (5*x³*y²+1)²
dz/dy= 3(5*x³*y²+1)² * 10x³y = 30 x³y * (5*x³*y²+1)²
dz/dx= 3(5*x³*y²+1)² * 15x²y²= 45x²y² * (5*x³*y²+1)²
dz/dy= 3(5*x³*y²+1)² * 10x³y = 30 x³y * (5*x³*y²+1)²