When adding polynomials, you must make sure you only combine terms with the same degree.
Add: `(4x^2 + 5x+6) + (3x^2 + 9x)`
First rearrange to place like terms together.
`(4x^2 + 3x^2) + (5x + 9x) + 6`
This will give:
`7x^2 + 14x + 6`
Math