Use double angle identity
We can relate '6x' to '3x' in the same way since 6 is 2*3.
Now sub into left side of identity. Simplify until it equals right side.
Answer:
Elimination isn't exactly the easiest for this situation. But since the equations are in the same form and not solved for the same variable, I would go with elimination. (If they were solved for the same variable, I would go with substitution.) It would require me to make a manipulation on both equations.
I would multiply first equation by 5 and second equation by -2. The reason I would do this is because the y's would have opposite coefficients and when you add opposites you get 0.
The new set of equations would look like this:
20x+10y=45
-14x-10y=2
But I will slope here since we aren't asked to solve it.
Some texts use the term linear combination instead of elimination. They are the same.
