Question

Решите пожалуйста 14-тое
Срочно

Answer 1

x + y = 3 , xy = 7

a) x²y + xy² = xy * (x + y) = 7 * 3 = 21

в) x² + y² = (x + y)² - 2xy = 3² - 2 * 7 = 9 - 14 = - 5

г) x³ + y³ = (x + y)*(x² - xy + y²) = (x + y)[(x + y)² - 2xy - xy] = (x + y)[(x + y)² - 3xy] =

= 3 * (3² - 3 * 7) = 3 * (9 - 21) = 3 * (- 12) = - 36

Answer 2

а) x²y+xy²= xy(x+y)= 7*3= 21

в) (x+y)²=3²

x²+2xy+y²=9

x²+y²=9-2xy

x²+y²= -5

г) (x+y)³=3³

x³+3x²y+3xy²+y³=27

x³+y³=27-3(x²y+xy²)

x³+y³= 27- 3*21

x³+y³= -36