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Mathematics 15 Online
OpenStudy (anonymous):

The graph below represents which system of inequalities? y less than or greater to -2x + 3 y less than or greater to x + 3 y greater than or equal to -2x + 3 y greater than or equal to x + 3 y less than or greater to -3x + 2 y less than or greater to -x + 2 y > -2x + 3 y > x + 3

OpenStudy (anonymous):

Vocaloid (vocaloid):

hint: ignore the green and yellow for now, just focus on the two black lines write the equations for the lines in point intercept form

OpenStudy (anonymous):

y=1/ 1/2+3

OpenStudy (anonymous):

?

Vocaloid (vocaloid):

uh... not quite

Vocaloid (vocaloid):

|dw:1443914795869:dw| lets focus on one line at a time. what is the equation of this line?

OpenStudy (anonymous):

ok

Vocaloid (vocaloid):

|dw:1443914881362:dw| write the equation for this line please

OpenStudy (anonymous):

y=3x-3 ? @Vocaloid

Vocaloid (vocaloid):

nope first find the slope of the graph

Vocaloid (vocaloid):

(x1,y1) = (-3,0) (x2,y2) = (0,3) slope = m = (y2-y1)/(x2-x1) = ?

OpenStudy (anonymous):

(0-3) and -3-0 @Vocaloid

Vocaloid (vocaloid):

keep going (0-3)/(-3-0) = ?

OpenStudy (anonymous):

-3 and -3

Vocaloid (vocaloid):

keep going

Vocaloid (vocaloid):

/ means divide...

Vocaloid (vocaloid):

-3/-3 = ?

OpenStudy (anonymous):

1

OpenStudy (anonymous):

@Vocaloid

Vocaloid (vocaloid):

good, so our slope is 1 now find the y-intercept

OpenStudy (anonymous):

3 @Vocaloid

Vocaloid (vocaloid):

good, so our equation is y = x + 3 now write an equation for the other line

OpenStudy (anonymous):

0,3 and -1, 2?

OpenStudy (anonymous):

@Vocaloid

Vocaloid (vocaloid):

uh not quite

Vocaloid (vocaloid):

look at the graph and pick two points on the line on the right

Vocaloid (vocaloid):

|dw:1443916158259:dw|

OpenStudy (anonymous):

ill i can see is 3/ 1.5

OpenStudy (anonymous):

@Vocaloid

Vocaloid (vocaloid):

not quite...

Vocaloid (vocaloid):

two points are (0,3) and (2,-1) now calculate the slope between them

OpenStudy (anonymous):

-1

OpenStudy (anonymous):

@Vocaloid

OpenStudy (texaschic101):

slope = (y2 - y1) / (x2 - x1) (0,3)....x1 = 0 and y1 = 3 (2,-1)....x2 = 2 and y2 = -1 now we sub slope(m) = (-1 - 3) / (2 - 0) slope(m) = -4/2 slope(m) = -2 now we use y = mx + b slope(m) = -2 use either of your sets of points....(0,3)...x = 0 and y = 3 now we sub into the formula to solve for b, the y intercept 3 = -2(0) + b 3 = b so the equation for that line is : y = -2x + 3

OpenStudy (texaschic101):

now take your 2 lines... y = x + 3 and y = -2x + 3 notice that both lines are solid...this means they both contain equal signs. notice that both lines are shaded below the line....this means that both lines are less then <. so the inequalities that match the graph are : y <= x + 3 and y <= 2x + 3

OpenStudy (mathstudent55):

This is how you solve this quickly since we are given choices. 1. Both lines are solid; that means either >= or <=, but not > or <. 2. Both lines have the shaded area under the solid line. That means y <= ax + b. 3. Both lines have y-intercepts of 3. That means both inequalities are of the form y <= ax + 3 The only set of inequalities that satisfies all conditions above is choice A. Of course, this is assuming that where you wrote "less than or greater to" you really meant "less than or equal to."

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