How do you solve simultaneous equations that include negatives? - Answers

You solve simultaneous equations involving negatives the same way you solve simultaneous equations not involving negatives. You subtract an appropriately scaled version of one from the other in order to cancel the terms of one variable, solving for the other variable. Remember that multiplying by -1 will reverse the signs, so that can be a trick to being able to visualize the subtraction. An example... 3x - 2y = 7 4x + 4y = -3 Multiply the first equation by -2 and solve for x... -6x + 4y = -14 4x + 4y = -3 -------------------- -10x = -11 x = 1.1 Backsubstitute and solve for y 3x - 2y = 7 3.3 - 2y = 7 -2y = 3.7 y = -1.85 Its just a matter of keeping the signs straight and remembering that subtracting a minus means to add. You can also add the equations instead of subtracting, if it seems that would also cancel a term.