Mathematics Predictions/Thoughts (3 Viewers)

flowerp

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For the rate of change question, are we meant to have the negative in the answer like -365 leaves/day. I wrote decreasing at a rate of 365 leaves/day
That is correct - both decreasing at 365 etc. And rate of change=-365 etc are right. You only lose marks if you use a double negative, ie write decreasing at -365 :)
 

alussovsky

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for the national park question part ii, i completely missed out on the whole D^2 part of "show that x=2 is a minimum for D^2" aNd fREAKING DIFFERENTIATED D RATHER THAN D^2. i wanted to punch myself after i wrote "x=2 is a minimum for D, therefore it is a minimum for D^2"
 

flowerp

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NOOOOOO, I forgot to discard the negative 2 for the log question!!!
OMG SAME ! I used the rule e^lna = a instead of logging etc !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
 

hello288292

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NOOOOOO, I forgot to discard the negative 2 for the log question!!!
OMG SAME ! I used the rule e^lna = a instead of logging etc !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
Omg SAME I was so close to leaving it there but I when I was checking my answer, it gave a math error and I'm like crap I have to discard it
 

Saturday

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I'm going to let the tutoring centres do Q14 and before, but (c) is probably the hardest question in 14, so here's one possible solution:

Triangle AFE is isosceles because AF = FE (regular hexagon). Angle sum of a hexagon = (n-2)180 = 4*180 = 720. Again, it's a regular hexagon so angle AFE = 720/6 = 120. Therefore angle FEA = (180 - 120)/2 = 30 (base angles of an isosceles triangle are equal). So angle AED = 120 - 30 = 90 (adjacent angles). Therefore angle XED = 90 as well (adjacent angles on a straight line). So XED is a right triangle.

That means we can use right angle trig in XED. tan(angle DXE) = DE/EX = 1/EX. But also, angle DXE = angle FAE (alternate angles, AF || CX due to the symmetry of the regular hexagon). And angle FAE = 30 degrees (it's the other base angle of the isosceles triangle AFE). So tan30 = 1/EX; that is, 1/sqrt(3) = 1/EX. So EX = sqrt(3).
 
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That is correct - both decreasing at 365 etc. And rate of change=-365 etc are right. You only lose marks if you use a double negative, ie write decreasing at -365 :)
Yep! I confirmed this with a teacher who marks the HSC and he said both would receive the full mark
 

Saturday

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I would have probably skipped 14(c) if I was sitting the exam and come back to it at the end... it took me a lot of time to come up with that solution! And this is coming from someone who got 100% in his HSC for Maths Extension 1.
 

anerd

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I would have probably skipped 14(c) if I was sitting the exam and come back to it at the end... it took me a lot of time to come up with that solution! And this is coming from someone who got 100% in his HSC for Maths Extension 1.
Can you please do MCQ?
 
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I would have probably skipped 14(c) if I was sitting the exam and come back to it at the end... it took me a lot of time to come up with that solution! And this is coming from someone who got 100% in his HSC for Maths Extension 1.
This is how I did it (attached). It was definitely tricky but I stared at it during reading time and it somehow clicked
 

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Saturday

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I think these are the answers to the MCQ. I thought they were kind of tricky for a 2U paper. Sorry, no working:
  1. B
  2. D
  3. B
  4. C
  5. A
  6. C
  7. D
  8. C
  9. A
  10. B
 

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