(Integration), where did I go wrong? (1 Viewer)

[BlueGas]

Find the areas enclosed by the following parabolas and x-axis, include a sketch of the graph:

I did the question and I don't know what I did wrong, need help, thanks.

 

[FancyPenguin]

you did a - instead of a plus
2-2x-x-x^2 -> 2+2x-x-x^2

 

[Silly Sausage]

In before this goes for 3 pages:


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[hypermax]

Find the areas enclosed by the following parabolas and x-axis, include a sketch of the graph:

I did the question and I don't know what I did wrong, need help, thanks.

you expanded wrong, add like terms!!!!!

 

[BlueGas]

you did a - instead of a plus
2-2x-x-x^2 -> 2+2x-x-x^2

In before this goes for 3 pages:


=

=

I expanded wrong, but why am I meant to do plus instead of a minus? I did another question and I used the minus and still got the right answer. Here's the other question:

you expanded wrong, add like terms!!!!!

Woops, didn't realise that, thanks for that.

 

[BlueGas]

Nevermind, I know what I did wrong now, thanks guys!

 

[Silly Sausage]

Because you're adding the two areas together

 

[hypermax]

Your method is correct, the only time you should separate the equation is when your finding the area of a cubic or an odd function. But you will get to that later in the chapter

 

[BlueGas]

Your method is correct, the only time you should separate the equation is when your finding the area of a cubic or an odd function. But you will get to that later in the chapter

Yeah the odd/even function confuses me, although I haven't learnt about it yet but I'm upto the relating to y-axis part of the Intergration chapter, am I passed the odd/even function thing? Anyways, I think that next question I'm posting now relates to what you're talking about, I'm really getting frustrated because I'm getting the wrong answer, but for now, what did I do wrong in this question?

 

[hypermax]

Yeah the odd/even function confuses me, although I haven't learnt about it yet but I'm upto the relating to y-axis part of the Intergration chapter, am I passed the odd/even function thing? Anyways, I think that next question I'm posting now relates to what you're talking about, I'm really getting frustrated because I'm getting the wrong answer, but for now, what did I do wrong in this question?

Stick to the method you did on image 2

 

[BlueGas]

Stick to the method you did on image 2

Oh okay, but when do I minus and when do I plus? This question by the way was asking to find the area 'bounded', what do I do for enclosed and what do I do for bounded? They seem to confuse me.

 

[Silly Sausage]

Maybe you should try to reattempt the question if you haven't, then post if you're have difficulties.

 

[hypermax]

Oh okay, but when do I minus and when do I plus? This question by the way was asking to find the area 'bounded', what do I do for enclosed and what do I do for bounded? They seem to confuse me.

Its always minus and I think bounded and enclosed have the same mathematical meaning

 

[BlueGas]

Maybe you should try to reattempt the question if you haven't, then post if you're have difficulties.

I reattempted the question using the other method and still got an incorrect answer. What am I doing wrong? I don't understand.

 

[hypermax]

I reattempted the question using the other method and still got an incorrect answer. What am I doing wrong? I don't understand.

That question doesn't make sense. Are you sure you got the correct ordinates

 

[BlueGas]

That question doesn't make sense. Are you sure you got the correct ordinates

The question I'm trying to do is Question 13 in the picture I posted.

 

[FancyPenguin]

What quesiton are you doing?
(2-x)(1+x) =2+2x-x-x^2 AND NOT 2-2x-x-x^2

intergrating 2+x-x^2 gives you 2x+(x^2)/2-(x^3)/3
the sub in the x-intercepts

(2(2)+(2^2)/2 - (2^3)/3)-(2(1)+(-1^2)/2 -(/1^3)/3)

this gives you 4.5 for the first one, are you also doing the 2nd question now?


for the next question with 4x^2-1 I also got 0

 

[BlueGas]

What quesiton are you doing?
(2-x)(1+x) =2+2x-x-x^2 AND NOT 2-2x-x-x^2

intergrating 2+x-x^2 gives you 2x+(x^2)/2-(x^3)/3
the sub in the x-intercepts

(2(2)+(2^2)/2 - (2^3)/3)-(2(1)+(-1^2)/2 -(/1^3)/3)

this gives you 4.5 for the first one, are you also doing the 2nd question now?

I've already solved the error for the question you done, thank you anyway, I'm currently trying to figure out Question 13 in the photo I posted above.

 

[hypermax]

The question I'm trying to do is Question 13 in the picture I posted.

The question is worded very poorly and incorrect, skip it.

 

[BlueGas]

What quesiton are you doing?
(2-x)(1+x) =2+2x-x-x^2 AND NOT 2-2x-x-x^2

intergrating 2+x-x^2 gives you 2x+(x^2)/2-(x^3)/3
the sub in the x-intercepts

(2(2)+(2^2)/2 - (2^3)/3)-(2(1)+(-1^2)/2 -(/1^3)/3)

this gives you 4.5 for the first one, are you also doing the 2nd question now?


for the next question with 4x^2-1 I also got 0

0 isn't the answer though, that's what confuses me.