Question

The tables of ordered pairs represent some points on the graphs of two lines. What is the solution to the system of equations represented by the two lines?

Answer 1

x = -9 and y =. 5

Explanation:

(-2, 19) and (-1, 21)

Slope: (21-19)/(-1- -2) = 2

y-intercept = 21 - (2)(-1) = 23

a) y =2x + 23

(-2,-44) and (-1,-51)

Slope: (-51- - 44)/(-1- -2) = -7/1 = -7

y-intercept: -44-(-7)(-2)=-58

b) y = -7x - 58

Substitute y in equation a.

-7x-58 = 2x + 23

-9x = 81

x = -9

Substitute X by -9 in equation b: y = -7(-9) - 58= 5

y = 5

Answer 2

(-9, 5)

Explanation:

1. Find the equations of both lines (y = mx +b).

For the table on the left, we can see that the y-intercept is 23 (at x=0, y=23). Hence, b = 23. We can also see that the y-value for the left table increases by increments of 2, meaning that the slope (m) will be 2. Thus:

f1(x) = 2x + 23

For the right table, do the same thing. The table tells us that when x = 0, y = -58 (so b = -58). We also see that the y-value DECREASES in increments of 7, meaning that the slope, m = -7. Thus,

f2(x) = -7x - 58

2. Set the equations equal to each other to find the x-value at which the two equations will intersect.

2x + 23 = -7x - 58

9x = -81

x = -9

3. Plug your newfound x-value into any of the two equations to find the y-value at which both equations will intersect.

y = 2x + 23

y = 2(-9) + 23

y = 5

OR

y = -7x - 58

y = -7(-9) - 58

y = 5

ANSWER: At the point (-9, 5), the two lines intersect. Hence, the solution to the equation is (-9, 5).