2)
A = 9x² - 3xy² + x (x - y)
x = -1 ; y = -2
A = 9 x (-1)² - 3 x (-1) x (-2)² + (-1)² + (-1) x 2
A = 9 + 6 + 1 - 2
A = 14
3)
B = (a+b²) / 2ab²
a = 5/6 ; b = -1/3
B = (5/6 + (-1/3)²) / 2 x 5/6 x (-1/3)²
B = (5/6 + 1/9) / 10/6 x 1/9
B = (17/18) / (5/27) = 51/10 = 5,1
