Subtract x-y from the sum of x+3y and -3x-y?

(2a²b + 3b²) + (5a²b + 7b²) =

What should be subtracted from 8a²b² - 9a³+ 11y³ to get 6y³?

Which of the following is not a polynomial?

5a + 7a + 2b + 8b - a + 1 = ?

What should be subtracted from 8x⁴+14x³- 2x²+ 7x - 8,so that the resulting polynomial is exactly divisible by 4x²+3x-2?

(6x - 5) × (-3x) = ?