1 00:00:00,000 --> 00:00:00,620 2 00:00:00,620 --> 00:00:04,679 We're told to find the x- and y-intercepts for the graph of 3 00:00:04,679 --> 00:00:09,029 this equation: 2 y plus 1/3x is equal to 12. 4 00:00:09,029 --> 00:00:14,399 And just as a bit of a refresher, the x-intercept is 5 00:00:14,400 --> 00:00:17,240 the point on the graph that intersects the x-axis. 6 00:00:17,239 --> 00:00:21,109 So we're not above or below the x-axis, so our y value 7 00:00:21,109 --> 00:00:22,910 must be equal to 0. 8 00:00:22,910 --> 00:00:29,329 And by the exact same argument, the y-intercept 9 00:00:29,329 --> 00:00:32,289 occurs when we're not to the right or the left of the 10 00:00:32,289 --> 00:00:36,070 y-axis, so that's when x is equal to 0. 11 00:00:36,070 --> 00:00:38,579 So let's set each of these values to 0 and then solve for 12 00:00:38,579 --> 00:00:41,339 what the other one has to be at that point. 13 00:00:41,340 --> 00:00:46,080 So for the x-intercept, when y is equal to 14 00:00:46,079 --> 00:00:47,399 0, let's solve this. 15 00:00:47,399 --> 00:00:52,719 So we get 2 times 0, plus 1/3x is equal to 12. 16 00:00:52,719 --> 00:00:55,530 I just set y is equal to 0 right there, right? 17 00:00:55,530 --> 00:00:56,800 I put 0 for y. 18 00:00:56,799 --> 00:00:59,869 Well, anything times 0 is just 0, so you're just left with 19 00:00:59,869 --> 00:01:03,759 1/3x is equal to 12. 20 00:01:03,759 --> 00:01:08,120 To solve for x, you can think of it as either dividing both 21 00:01:08,120 --> 00:01:11,410 sides by 1/3, or we can multiply both sides by the 22 00:01:11,409 --> 00:01:13,019 reciprocal of 1/3. 23 00:01:13,019 --> 00:01:15,719 And the reciprocal of 1/3 is 3, or you can even think of it 24 00:01:15,719 --> 00:01:17,185 as 3 over 1. 25 00:01:17,185 --> 00:01:19,890 So times 3 over 1. 26 00:01:19,890 --> 00:01:24,250 And so we're left with 3 times 1/3, that just cancels out, so 27 00:01:24,250 --> 00:01:28,689 you're left with x is equal to 12 times 3, or 28 00:01:28,689 --> 00:01:30,549 x is equal to 36. 29 00:01:30,549 --> 00:01:33,340 So when y is equal to 0, x is 36. 30 00:01:33,340 --> 00:01:40,520 So the point 36 comma 0 is on the graph of this equation. 31 00:01:40,519 --> 00:01:43,359 And this is also the x-intercept. 32 00:01:43,359 --> 00:01:46,640 Now, let's do the same thing for the y-intercept. 33 00:01:46,640 --> 00:01:55,060 So let's set x equal 0, so you get 2y plus 1/3, times 0 is 34 00:01:55,060 --> 00:01:56,320 equal to 12. 35 00:01:56,319 --> 00:01:59,599 Once again, anything times 0 is 0. 36 00:01:59,599 --> 00:02:04,469 So that's 0, and you're just left with 2y is equal to 12. 37 00:02:04,469 --> 00:02:09,008 Divide both sides by 2 to solve for y, and you're left 38 00:02:09,008 --> 00:02:13,639 with y is equal to 12 over 2, is 6. 39 00:02:13,639 --> 00:02:17,635 So the y-intercept is when x is equal to 0 and 40 00:02:17,635 --> 00:02:20,650 y is equal to 6. 41 00:02:20,650 --> 00:02:22,770 So let's plot these two points. 42 00:02:22,770 --> 00:02:24,780 I'll just do a little hand-drawn graph, and make it 43 00:02:24,780 --> 00:02:28,180 clear what the x- and the y-intercepts are. 44 00:02:28,180 --> 00:02:32,150 So let me draw-- that's my vertical axis, and that is my 45 00:02:32,150 --> 00:02:36,629 horizontal axis-- and we have the point 36 comma 0. 46 00:02:36,629 --> 00:02:39,659 So this is the origin right here, that's the x-axis, 47 00:02:39,659 --> 00:02:40,669 that's the y-axis. 48 00:02:40,669 --> 00:02:43,750 The point 36 comma 0 might be all the way over here. 49 00:02:43,750 --> 00:02:47,270 So that's the point 36 comma 0. 50 00:02:47,270 --> 00:02:54,460 And if that's 36, then the point 0, 6 might be right 51 00:02:54,460 --> 00:02:55,210 about there. 52 00:02:55,210 --> 00:02:57,939 So that's the point 0, 6. 53 00:02:57,939 --> 00:03:01,389 And the line will look something like this. 54 00:03:01,389 --> 00:03:04,809 55 00:03:04,810 --> 00:03:06,810 I'm trying my best to draw a straight line. 56 00:03:06,810 --> 00:03:11,360 And notice where the line intercepted or intersected the 57 00:03:11,360 --> 00:03:15,330 y-axis, that's the y-intercept, x is 0, because 58 00:03:15,330 --> 00:03:17,190 we're not to the right or the left of it. 59 00:03:17,189 --> 00:03:21,750 Where the line intersected the x-axis, y is 0, because we're 60 00:03:21,750 --> 00:03:24,300 not above or below it. 61 00:03:24,300 --> 00:03:24,332