One linear equation: Ax + By = C (A, B, and C are constants) Another linear equation: Dx + Ey = F (D, E, and F are constants) Their sum: (A+D)x + (B+E)y = (C + F) The coefficients (A+D), (B+E), and (C+F) are still constants, so the sum is still a linear equation.
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I guess you mean, you want to add two equations together. The idea is to do it in such a way that one of the variables disappears from the combined equation. Here is an example:5x - y = 15 2x + 2y = 11 If you add the equations together, no variable will disappear. But if you first multiply the first equation by 2, and then add the resulting equations together, the variable "y" will disappear; this lets you advance with the solution.
Solving linear equations using linear combinations basically means adding several equations together so that you can cancel out one variable at a time. For example, take the following two equations: x+y=5 and x-y=1 If you add them together you get 2x=6 or x=3 Now, put that value of x into the first original equation, 3+y=5 or y=2 Therefore your solution is (3, 2) But problems are not always so simple. For example, take the following two equations: 3x+2y=13 and 4x-7y=-2 to make the "y" in these equations cancel out, you must multiply the whole equation by a certain number.
Multiply the top equation by -3 and the bottom equation by 2.
You multiply one or both equations by some constant (especially chosen for the next step), and add the two resulting equations together. Here is an example: (1) 5x + 2y = 7 (2) 2x + y = 3 Multiply equation (2) by -2; this factor was chosen to eliminate "y" from the resulting equations: (1) 5x + 2y = 7 (2) -2x -2y = -6 Add the two equations together: 3x = 1 Solve this for "x", then replace the result in any of the two original equations to solve for "y".
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