[tex] a^{2}+2a-3=0[/tex]
Add 3 to both sides, and you get:
[tex]( a^{2}+2a -3) +3=0+3[/tex]
Next you want to identify the like terms an group them together.
You will get:
[tex] a^{2} +2a + (-3+3)= 0 +3[/tex]
Now, you can combine (-3+3) together and you get 0
Now you have:
[tex]a ^{2}+2a=3
[/tex]
And, that's your answer. If you have any questions, just ask, and I hope this helps! :)