Explain how you could add 678 + 303 using mental math
2 answers:
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Answer:
- Only one solution
- (x, y) = (-0.8, -3.6)
Step-by-step explanation:
You know there is only one solution because the ratio of x- and y-coefficients is different in the two equations. That means the lines will have different slopes, so must intersect in exactly one point.
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The y-coefficients are opposites, so you can eliminate the y-variable by adding the equations:
(2x -y) + (3x +y) = (2) + (-6)
5x = -4
x = -4/5 = -0.8
Substituting this into the second equation, we have ...
3(-0.8) +y = -6
y = -3.6 . . . . . . . add 2.4 to both sides
The solution is (x, y) = (-0.8, -3.6).
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You can also find the solution by graphing (or using a graphing calculator).
