adding and subtracting polynomials.

$$Add:\ \ \left(9x^3+5x^2-3x\right)+\left(4x^3-8x^2+7x\right)$$  

$$Add:\ \ \left(-4k^4+14+3k^2\right)+\left(-3k^4-14k^2-8\right)$$  

$$Add:\ \ \left(9r^3+5r^2+11r\right)+\left(-2r^3+9r-8r^2\right)$$  

$$Subtract:\ \ \left(3r^4+4r^3\right)-\left(r^4-5r^3\right)$$  

$$Subtract:\ \ \left(6x^4-5x^3+2x^2-8x\right)\ -\ \left(4x^4+5x^3+3x^2+12x\right)$$  

$$Subtract:\ \ \left(13a^2-6a^5-2a\right)-\left(-10a^2-11a^5+9a\right)$$  

Simplify: (-9a + 12 - 6b) + (3b + 21a - 2)

(a)  

Simplify: (3x² - 3x + 2) + (x² - 2x + 1)

Simplify:

(5x + x² - 4) - (4x - x² + 6) 

Add these polynomials:

(5x + 2) + (4x + 5)