Solving Systems by Elimination (Addition)

When to use: when both equations are in standard form (ax + by = c) and the coefficients of one variable are easy to cancel. Steps: 1. Line up the equations vertically (same variables aligned) 2. Multiply one or both equations so that one variable's coefficients are opposites 3. Add the equations to eliminate that variable 4. Solve the remaining one-variable equation 5. Back-substitute to find t…

Example: Solve: [formula]

Look for the easiest cancellation: 1. Coefficients already opposite: just add (like +2y and -2y) 2. Coefficients already equal: subtract (or multiply one by -1 then add) 3. One coefficient is a multiple: multiply the smaller by a factor 4. Neither easy: multiply both equations by different factors Pro tip: eliminate whichever variable requires the least multiplication.