a) 2x²-xy²-5x²+2xy² dla= x= 1/3, i y= 9 b)-1/2x³y-2/3xy+1/2x³y-1/3xy

a) 2x² - xy² - 5x² + 2xy² = - 3x² + xy² dla x = ⅓ i y = 9 = - 3 * (⅓)² + ⅓ * 9² = - 3 * ¹/₉ + ⅓ * 81 = - ⅓ + 27 = 26²/₃ b) -½x³y - ⅔xy + ½x³y - ⅓xy = - xy dla x = ⅓ i y = 9 = - ⅓ * 9 = - 3