AlgebraMediumFinding the input that gives a specified output
Algebra practice question
A line in the xy-plane passes through the point (1, 4) and has slope −3. For what value of x is y equal to −11 on this line?
Answer: 6
y − 4 = −3(x − 1). Set y = −11: −15 = −3(x − 1) → x − 1 = 5 → x = 6.
Common wrong answers
- If you answered 5
- 5 is x − 1, forgetting to add the 1.
- If you answered -4
- −4 comes from x − 1 = −5, dropping a sign.
- If you answered -11
- −11 is the y-value, not x.
More Algebra questions
- Medium
A system: 2x + y = 11 and x − y = 1. What is the value of x + y? - Medium
Which of the following describes all solutions to 4x − 9 ≤ 2x + 5? - Medium
A phone's battery percentage is modeled by P = 100 − 8t, where t is the number of hours since it was unplugged… - Medium
If y = 2x − 1 and 3x + y = 14, what is the value of x? - Medium
If |2x − 3| = 7, what is the sum of all possible values of x? - Medium
Line k has equation y = (2/3)x + 1. Which equation represents a line perpendicular to line k?
Not affiliated with the College Board. SAT is a trademark of the College Board.