314.
1) 4a^2 - (6a^2 - 2ab) + (3ab + 2a^2) = 5ab
4a^2 - 6a^2 + 2ab + 3ab + 2a^2 = 5ab
-2a^2 + 5ab + 2a^2 = 5ab
5ab = 5ab
2) (9x^6 - 4x^3) - (x^3 - 9) - (8x^6 - 5x^3) = x^6 + 9
9x^6 - 4x^3 - x^3 + 9 - 8x^6 + 5x^3 = x^6 + 9
x^6 - 5x^3 + 9 + 5x^3 = x^6 + 9
x^6 + 9 = x^6 + 9
316.
(5.7a^2 - 2.1ab + b^2) - (3.9ab - 0.3a^2 + 2b^2)
5.7a^2 - 2.1ab + b^2 - 3.9ab + 0.3a^2 - 2b^2
6a^2 - 6ab - b^2
a= -1 b = 5
6*(-1)^2 - 6*(-1)*5 - 5^2
6 + 30 - 25
11
(5m^2 *n - m^3) +7m^3 - (6m^3 - 3m^2*n)
5m^2 *n - m^3 +7m^3 - 6m^3 + 3m^2*n
8m^2 *n
m= -2/3 n = 3/16
8*(-2/3)^2 * 3/16
8* 4/9 * 3/16
2/3