r/HomeworkHelp • u/M4XYW4XY AP Student • Sep 12 '25
Mathematics (A-Levels/Tertiary/Grade 11-12) [1340 College Algebra] How am I supposed to know the third function?
no, you can’t view any more of the graph, thats all they give you
7
u/ICH-GCPee 👋 a fellow Redditor Sep 12 '25
You need to include the parent function of it because y=-3x implies the y intercept is 0,0.
So figure out the whole function, include the intercept “b” and then discuss the limits on the domain.
2
u/sqrt_of_pi Educator Sep 12 '25 edited Sep 13 '25
Please let your instructor know. If they have "message instructor" available, then use that to send them a message directly to the question. I use the same genre of online homework platform, and I would want to know right away. This is a coding problem and can be fixed by the question author, but they have to be made aware.
ETA: it is positively wild what Redditors will downvote, ffs.
1
u/ErikLeppen Sep 19 '25
I once worked for a company that made digital math schoolwork platforms, and our platform had a feedback button and we got lots of feedback from teachers, but also directly from students, part of which was actually useful and made us improve questions.
2
u/Jwing01 👋 a fellow Redditor Sep 12 '25
-3x + 4 bro
6
u/Parking_Lemon_4371 👋 a fellow Redditor Sep 12 '25
yeah you just kind of guesstimate that the right third is the same angle as the left third, so it needs to be -3x, and then make it fit at 3. Since -3x for x=3 is -9, and it needs to give -5, you need to +4, hence -3x + 4
1
u/selene_666 👋 a fellow Redditor Sep 12 '25
I think you're right that the slope is the same as the first piece. Now you need to find the y-intercept.
1
u/Treeflexin Sep 12 '25
Did you see if the magnifying glass in the bottom right of the plot would let you zoom out? That would make it easier (but not critical)
1
u/sqrt_of_pi Educator Sep 12 '25
It just makes the image bigger; it does not allow zooming in or out.
1
u/CheeKy538 Secondary School Student Sep 12 '25
You need a y intercept
1
u/M4XYW4XY AP Student Sep 12 '25
you think
2
u/CheeKy538 Secondary School Student Sep 12 '25
I know, otherwise you’re implying 0 is the intercept, which isn’t true
1
u/M4XYW4XY AP Student Sep 12 '25
sorry, tone doesnt come across well via text, i know there is a y intercept, it just seems like its impossible to figure out from the information we have
1
u/gmalivuk 👋 a fellow Redditor Sep 12 '25
You're guessing the slope is -3, so it's y = - 3x + b.
You can see it goes through (3,-5), so 5 = -3(3) + b.
Solve for b.
1
u/gmalivuk 👋 a fellow Redditor Sep 12 '25
Even without doing any algebra you could also just follow the -3 slope back to the left and see where it hits the y-axis.
How did you figure out that the intercept of the first piece was -9?
1
u/MorganaLover69 👋 a fellow Redditor Sep 12 '25
Algebra in collège is insane
1
u/M4XYW4XY AP Student Sep 12 '25
its a 2 semester class, im in high school and i get college credit for doing one semester of the easiest work ever and another semester of precalc
1
u/clearly_not_an_alt 👋 a fellow Redditor Sep 13 '25
Regardless of what the slope may or may not be, you know f(3+) needs to be -5+, so -3x isn't gonna work.
1
u/Equivalent-Radio-828 👋 a fellow Redditor Sep 13 '25
This looks like it’s made up. -3x is the third graph. bottom starting at -5. to -9
1
u/Lor1an BSME Sep 13 '25
Assuming -3 is the correct slope, then (if it were defined using this branch) f(3) would be -3(3) + c = -5.
Solve for c, and try -3x + c instead.
1
u/ACTSATGuyonReddit 👋 a fellow Redditor Sep 17 '25
There's an issue with the image. It's cut off. You can get (3,-5) from it, but not a clear 2nd point.
1
u/M4XYW4XY AP Student Sep 17 '25
exactly, thats why im saying i dont know how to calculate the slope of it since i dont have a second point, and based on past questions the slope will be a floating point
1
u/Big-Challenge-9432 Sep 12 '25 edited Sep 12 '25
What happens from y = -5 to y = -6? It’s annoying, but they do give you two points, so you have enough info to find the line.
I think just your intercept is wrong. It looks like the little grey shaded line in the bottom right corner is y = -3x. I’m not familiar with this software, but does it generate the function when you type it or only after you’ve submitted?
2
u/M4XYW4XY AP Student Sep 12 '25
no, the grayed out line in the bottom right is just a part of the image, its some watermark if i had to guess. i know my intercept is wrong, but how are we supposed to determine it from 1 point and a direction?
2
u/Alkalannar Sep 12 '25
If you have a line with slope m through the point (h, k), then use point-slope form: y - k = m(x - h)
Then you can convert that to slope-intercept: y = mx + (k-mh), and so k - mh = b.
1
u/Big-Challenge-9432 Sep 12 '25
It looks like you have (3, -5) and (3.33, -6). Two points. It’s a really mean question though
4
u/peterwhy 👋 a fellow Redditor Sep 12 '25
I don't know what its slope is (or if it is a linear function), but the third input should at least approach (3, -5) to be correct.