Integration question (1 Viewer)

highkeydropout

Member
Hi, does anyone know how to solve:

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highkeydropout

Member
i got 21 aswell, but I thought we subtract the bottom two from the area of the top? not sure tho

qUiCkMaThS

New Member
well, idk what I've done wrong, but if you find it, just point it out:

A1 + A2 + A3 = ATotal
A2 + A3 = 5A1/ 2

Since A1 = 3 x 2 = 6

ATotal = 15+6 = 21

i got 21 aswell, but I thought we subtract the bottom two from the area of the top? not sure tho
I've forgotten whether 'evaluate' changes what the question is asking....sorry about that!

highkeydropout

Member
well, idk what I've done wrong, but if you find it, just point it out:

A1 + A2 + A3 = ATotal
A2 + A3 = 5A1/ 2

Since A1 = 3 x 2 = 6

ATotal = 15+6 = 21

I've forgotten whether 'evaluate' changes what the question is asking....sorry about that!
no problem!! that's exactly what I got, it may be an error in the question, thank you!!

-15?

Last edited:

B1andB2

pyjama
A1=6
A2= 3
A3 = 5(3x2)-2(3)/2 = 12

when you evaluate the integral (not the same as finding area) you consider the fact that below= negative

so solving the integral = -6+3-12 = -15

highkeydropout

Member
A1=6
A2= 3
A3 = 5(3x2)-2(3)/2 = 12

when you evaluate the integral (not the same as finding area) you consider the fact that below= negative

so solving the integral = -6+3-12 =15
yesss that makes sense, thank you tooo!!

B1andB2

pyjama
are you sure it's 15?

it seems to be -15 the way im doing it

highkeydropout

Member
are you sure it's 15?

it seems to be -15 the way im doing it
my mistake it is -ve, sorry!

notme123

Member
are you sure it's 15?

it seems to be -15 the way im doing it
I think it's -21. A1 should be -6 I think, not +6.

B1andB2

pyjama
I think it's -21. A1 should be -6 I think, not +6.
A1 means the area so it should be positive when you use it to find area 3

when you solve the integral though, you take the negative because it’s below

notme123

Member
A1 means the area so it should be positive when you use it to find area 3

when you solve the integral though, you take the negative because it’s below
Oh ok with the equation they give you they mean areas so it's positive. Understood

YonOra

Well-Known Member
A1=6
A2= 3
A3 = 5(3x2)-2(3)/2 = 12

when you evaluate the integral (not the same as finding area) you consider the fact that below= negative

so solving the integral = -6+3-12 = -15
How'd u get A2 to be 3. Having an elderly moment

B1andB2

pyjama
How'd u get A2 to be 3. Having an elderly moment
area of a triangle is half breadth times height

notme123

Member
How'd u get A2 to be 3. Having an elderly moment
$\bg_white A2=\frac{1}{2} * 3 * 2=3$

YonOra

Well-Known Member
No i was about to delete it. I thought A3 was A2 and i was like what

YonOra

Well-Known Member
$\bg_white A2=\frac{1}{2} * 3 * 2=3$
Year 7 maths coming to bite me