AlgebraMediumIntersection of two lines
Algebra practice question
In the xy-plane, the graphs of y = 2x − 1 and y = −x + 8 intersect at the point (a, b). What is the value of b?
- A. 5Correct
- B. 3
- C. 7
- D. 9
Answer: A. 5
Set 2x − 1 = −x + 8: 3x = 9, so x = 3, and y = 2(3) − 1 = 5.
Why the other answers are wrong
- B. 3
- 3 is the x-coordinate a; the question asks for b = 5.
- C. 7
- 7 is y on the first line at x = 4; the lines cross at x = 3.
- D. 9
- 9 is 3x during the solving, not the y-value.
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