A(x) = 2x^4 - 5x ³ + 7x - 5 + 4x ³ + 3x ² + 2x + 3
=2x^4+( - 5x ³+ 4x ³)+(7x+ 2x)+3x^2+3
=2x^4-1x^3+9x+3x^2+3
=2x^4-1x^3+3x^2+9x+3
B(x) = 5x^4 - 3x ³ + 5x - 3x^4 - 2x³ + 9 - 6x
=(5x^4- 3x^4)+(-3x^3-2x^3)+(5x- 6x)+9
=2x^4-5x^3+1x+9
a) B(x)- C(x)
=(2x^4-5x^3+1x+9)-(x^4 + 4x ² + 5)
=2x^4-5x^3+1x+9+x^4 - 4x ² - 5
=(2x^4+x^4)-5x^3+1x+(9-5)- 4x ²
=3x^4-5x^3+1x+4- 4x ²
=3x^4-5x^3- 4x ²+1x+4