How To Add Polynomial Fractions With Variables

now, let's thinkabout expressions with more than one variable. so say i had theexpression a plus-- i'll do a reallysimple one, a plus b. and i want to evaluate thisexpression when a is equal to 7

How To Add Polynomial Fractions With Variables, and b is equal to 2. and i encourage you to pausethis and try this on your own. well, wherever we seethe a, we would just replace it with the 7.

and wherever we see the b,we'd replace it with the 2. so when a equals7 and b equals 2, this expressionwill be 7 plus 2, which, of course, is equal to 9. so this expressionwould be equal to 9 in this circumstance. let's do a slightlymore complicated one. let's say we have the expressionx times y minus y plus x. actually, let's make it plus 3x.

or another way of sayingit plus 3 times x. so let's evaluate this when x isequal to 3 and y is equal to 2. and once again, i encourageyou to pause this video and try this on your own. well, everywhere we see anx, let's replace it with a 3. every place we see a y,let's replace it with a 2. so this is going tobe equal to 3 times y. and y is 2 in this case. 3 times 2 minus 2plus this 3 times x.

but x is also now equal to 3. so what is thisgoing to be equal to? well, this is going to beequal to 3 times 2 is 6. this 3 times 3 is 9. so it simplifiesto 6 minus 2, which is 4, plus 9, whichis equal to 13. so in this case,it is equal to 13.