Use Logic with Intersecting Lines problems
Sometimes, you can use simple logic to answer multiple choice problems. Take the following question.
At what (x,y) coordinate point do the following 2 lines intersect? y=3x-3 and y=2x+1
a) (4, -9) b) (-4, 9) c) (4, 9) d) (0, 0)
If two lines intersect, they must have the same y values at that intersecting x point. Think of two lines crossing. At the point where they cross, they have the same (x,y) point. Look at option a. If I plug x=4 into the two equations, I should get the same answer.
y = 3(4) - 3 = 12 - 3 = 9
y = 2(4) + 1 = 8 + 1 = 9
OK, so I know x must be 4 and the result when I plug x = 4 in is 9. So, the answer is c) (4,9)
Knowing what the question is asking is key (i.e. understanding the x,y graph and intersecting lines). If you didn't really know and just followed some equation to get the answer, you may be spending too much time on the problem.
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