Combine like terms11) x^2 + 3x - 5 + x^2 - 2x - 5

Like terms are those terms whose variables are the same, and those variables appear with the same exponents.
In the given expression:
[tex]x^2+3x-5+x^2-2x-5[/tex]There are 6 terms in total. Notice that there are two quadratic terms:
[tex]x^2\text{ and }x^2[/tex]There are two linear terms:
[tex]3x\text{ and }-2x[/tex]And there are two constant terms:
[tex]-5\text{ and }-5[/tex]To combine like terms, add their coefficients. If a term does not have an explicit coefficient, it is equal to 1.
Then:
[tex]\begin{gathered} x^2+x^2=2x^2 \\ 3x-2x=x \\ -5-5=-10 \end{gathered}[/tex]Therefore:
[tex]x^2+3x-5+x^2-2x-5=2x^2+x-10[/tex]