medicalsupernova
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#41
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#41
(Original post by Kakakaty)
I'm not sure what else to do, I keep getting the same answer of A = 3 and for B = 2.5
For A:
Pick two points on the graph. Example: (0,4) and (6,6)
Then calculate the change in x and then calculate the change in y
Now use the values you have to calculate the gradient which is change in y over change in x.

For B:
Pick two points on the graph. Example (0,10) and (4,0)
Then calculate the change in x and the change in y again. This time you'll see that the change in y is negative because you do 0 - 10 = -10
Now use the values you got for B to calculate the gradient which is change in y over change in x. Your value here will be negative.

After that, there is a rule that you use to show if two lines are perpendicular
the gradient of the first line multiplied by the gradient of the second line = -1 (and this means they are perpendicular)
So m1 x m2 = -1 if they are perpendicular
So for the values you have substitute it into m1 x m2 and find the value.
If they are reciprocals of each other then they always multiply to give -1.

Hope this helps!
Last edited by medicalsupernova; 1 week ago
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DFranklin
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I'm not sure a different method is going to be that helpful, but you don't need to deal with gradients (let alone mention trig functions) to answer this.

The squares on the grid are at right angles. For line A, if you go across 6 units, you go up 2 units. For B to be perpendicular, it would have to be that if you go across 2 units, you go down 6 units (think about what happens if you rotate going one unit across/up by 90 degrees). Since you actually go down by 5, they're not perpendicular.
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