12.
Add like terms from both trinomials:
[tex]4x^{2} + -2x^{2} = 2x^{2}[/tex]
[tex]2x + -5x = -3x[/tex]
[tex]-1 + 3 = 2[/tex]
Combine these terms to get a new trinomial as your answer:
[tex]2x^{2} - 3x + 2[/tex]
13.
Subtract like terms from both trinomials (note that subtracting a negative is the same as adding it as a positive):
[tex]3x^{2} - 5x^{2} = -2x^{2}[/tex]
[tex]-8x - -11x = -8x + 11x = 3x[/tex]
[tex]-1 - -1 = -1 + 1 = 0[/tex]
0 can be left out of the answer.
Combine these terms to get a binomial as your answer:
[tex]-2x^{2} + 3x[/tex]
