Question

Подскажите плиз:
2)mn-2/5m^2+3mn-3/5m^2+2m^2
4)3,7a^2b-3ab+2ab^2-1,2a^b-1,2a^2b-2ab^2

-0,25y^2=
При у =, - 4

-2а^3б=(. ) ^3

Answer 1

$mn - \frac{2}{5} {m}^{2} + 3mn - \frac{3}{5} {m}^{2} + 2 {m}^{2} = 4mn + {m}^{2} \\ 3.7 {a}^{2} b - 3ab + 2a {b}^{2} - 1.2ab - 1.2 {a}^{2} b - 2a {b}^{2} =2.5 {a}^{2}b - 4.2ab \\ - 0.25 {y}^{2} = - 0.25 \times ( - 4 {)}^{2} = - 0.25 \times 16 = - 4$