How to find intersection from -8x+3y=11 and y=3x+4
2 answers:
Answer:
(-1, 1)
Step-by-step explanation:
It's somewhat difficult to find the point of intersection when graphing these by hand, but a graphing calculator can show it easily.
The lines intersect at (-1, 1).
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You are given an expression for y, which makes it easy to use <em>substitution</em> as a solution method. Using the second equation to substitute for y in the first equation, we get ...
-8x +3(3x +4) = 11
x +12 = 11 . . . . simplify
x = -1 . . . . . . . subtract 12
Substituting back into the second equation, we find y to be ...
y = 3(-1) +4 = 1
The lines intersect at (x, y) = (-1, 1).
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<em>Additional comment</em>
The slopes are 8/3 and 3. When hand-drawn lines have nearly the same slope, it is difficult to tell exactly where they intersect. Of course, a graphing calculator does not have the problem of finite line width and an apparent long region of intersection. It can pinpoint the intersection exactly.
Of course, "substitution" is not the only way this system of equations can be solved. However, for this system, it is one of the easiest when doing the solution by hand.
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