Masaken
Unknown Member
I still have no idea how to know which statements are true even though my teacher explained it, help?? (answer is C I think but I don't get how to get there)
vectors mcq (1 Viewer)
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Just go through each of them
the first one is true because the triangle inequality
has equality when a and b are in the same direction.
second is true by the first one. Assume b is opposite direction to a, so -b is same direction as a. then sub -b into the first equation which is true and you'll get the second equation. so second eqn is also true.
third is false: counter example is (3,0) and (3,0). Sub these in for a and b you get 3 + 3 = 0 which is false.
fourth is false: counter example a = (3,0) and b = (5,0). subbing in you get 3 - 5 = 2 which again is false.
I think the answer is B
the first one is true because the triangle inequality
second is true by the first one. Assume b is opposite direction to a, so -b is same direction as a. then sub -b into the first equation which is true and you'll get the second equation. so second eqn is also true.
third is false: counter example is (3,0) and (3,0). Sub these in for a and b you get 3 + 3 = 0 which is false.
fourth is false: counter example a = (3,0) and b = (5,0). subbing in you get 3 - 5 = 2 which again is false.
I think the answer is B
Vall
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- 2022
If the left hand side of the fourth one had absolute value signs around it, it would be true
Masaken
Unknown Member
so when i look at questions like these all i have to do is just find counter-examples which prove it false?Just go through each of them
the first one is true because the triangle inequality
second is true by the first one. Assume b is opposite direction to a, so -b is same direction as a. then sub -b into the first equation which is true and you'll get the second equation. so second eqn is also true.
third is false: counter example is (3,0) and (3,0). Sub these in for a and b you get 3 + 3 = 0 which is false.
fourth is false: counter example a = (3,0) and b = (5,0). subbing in you get 3 - 5 = 2 which again is false.
I think the answer is B
always a good ideas with these types of q but these types of questions are quite rare. I've never seen one in the hsc where they ask which ones, or how many are correct. they often ask which is true and there's only one correct one, in that case counterexamples would be helpful as well.