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2) Find \(b\). Plug (x,y) of either given point into equation. Example (-1,0): \(y=3x+b\) \(0=3(-1)+b\) \(0=-3+b\) \(b=3\) Plug value of \(b\) into equation
3) Full equation of line \(k\) is \(y=3x+3\). Every point (x, y) [and (n, 21)] on a line must satisfy the equation of the line.
4) Point (n, 21) lies on line \(k\) \(n =?\) (n = x-coordinate). Plug in (n, 21) \(y=3x+3\) \(21=3n+3\) \(18=3n\) \(n=6\)
Answer A
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Re: In the xy-coordinate system, points (2, 9) and (-1, 0) lie on line k.
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23 Aug 2018, 22:06
Bunuel wrote:
In the xy-coordinate system, points (2, 9) and (-1, 0) lie on line k. If the point (n, 21) lies on line k, what is the value of n?
A. 6 B. 7 C. 8 D. 9 E. 10
Simply use the concept of slope (which many of us think of as Rise/Run) - It is the change in y co-ordinate for a unit change in x co-ordinate) (2, 9), (-1 , 0) - When x co-ordinate reduces by 3 units, y co-ordinate reduces by 9 units (3 times). (-1, 0), (n, 21) - So when y co-ordinate increase by 21 units, x co-ordinate will increase by 7 units (1/3). So n = 6
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90% (01:23) correct 
