A level maths helppppWatch

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Thread starter 1 week ago
#1
Points A and B have coordinates (1,5) and (-2,y) respectively.
1.Find an expression for the gradient of the straight line AB.
Point C has coordinates(2,-3). The angle ABC is 90 degrees
2.Find the possible values of y
I got y-5/-3 for part 1 but I don't know how to do 2 someone pls help 0
1 week ago
#2
(Original post by random88)
Points A and B have coordinates (1,5) and (-2,y) respectively.
1.Find an expression for the gradient of the straight line AB.
Point C has coordinates(2,-3). The angle ABC is 90 degrees
2.Find the possible values of y
I got y-5/-3 for part 1 but I don't know how to do 2 someone pls help ABC is 90 degrees therefore the gradients AB and BC multiply to give -1
1
Thread starter 1 week ago
#3
(Original post by RDKGames)
ABC is 90 degrees therefore the gradients AB and BC multiply to give -1
Yeah I know that so I got the gradient of BC to be 3/y-5 but I don't know how to get y
0
1 week ago
#4
(Original post by random88)
Yeah I know that so I got the gradient of BC to be 3/y-5 but I don't know how to get y
Form an equation, using what RDKGames said
1
Thread starter 1 week ago
#5
(Original post by AGrizzlyBearo)
Form an equation, using what RDKGames said
Oh right I get it now thank you!
1
Thread starter 1 week ago
#6
(Original post by AGrizzlyBearo)
Form an equation, using what RDKGames said I think I did this wrong 😬
0
1 week ago
#7
(Original post by random88) I think I did this wrong 😬
I think I mislead you a bit. (Woops)

The equation you did will simplify down to -1 = -1, which has an infinite number of solutions. That happens because the same values are being used in the equation.
(Which are the values of point A and point B)

To use the information about angle ABC being 90, you need to use the values for point C as well.

--- --- --- --- --- --- --- --- ---
So first work out the gradient of AB in terms of y ( using points A and B) (you've already done this)

Then work out the perpendicular gradient of BC in terms of y (only using points B and C)

Now you can form an equation using the fact
Grad of AB times perpendicular Grad of BC = -1

Or you can do :
Grad of AB = perpendicular Grad of BC
(I would use this one)
0
Thread starter 1 week ago
#8
(Original post by AGrizzlyBearo)
I think I mislead you a bit. (Woops)

The equation you did will simplify down to -1 = -1, which has an infinite number of solutions. That happens because the same values are being used in the equation.
(Which are the values of point A and point B)

To use the information about angle ABC being 90, you need to use the values for point C as well.

--- --- --- --- --- --- --- --- ---
So first work out the gradient of AB in terms of y ( using points A and B) (you've already done this)

Then work out the perpendicular gradient of BC in terms of y (only using points B and C)

Now you can form an equation using the fact
Grad of AB times perpendicular Grad of BC = -1

Or you can do :
Grad of AB = perpendicular Grad of BC
(I would use this one)
This worked great thank you 😊
0
1 week ago
#9
(Original post by random88)
This worked great thank you 😊
No problem : D
0
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