SHM Help, when do I take displacement as positive/negative?

Hey guys,
I'm taking M3 and concerning the SHM topic I'm having trouble in discerning when to take a displacement as positive or negative for certain questions. Is x negative when its below the equilibrium point in every question? E.g http://www.thestudentroom.co.uk/attachment.php?attachmentid=348767&d=1419287287 In questions 3 x has to be taken as -1 rather than +1, why?

Reply 1

Compost

Original post by Mjmuk

As long as you are consistent in your choice of positive and negative direction for all values affacted by direction throughout the question then it doesn't matter.

Reply 2

Mjmuk

Original post by Compost

As long as you are consistent in your choice of positive and negative direction for all values affacted by direction throughout the question then it doesn't matter.

I thought as much but in the question I attached there are no other values required eg Acceleration, Velocity which would tell me which direction is positive, this meant I could choose either a negative or a positive value for dsiplacement but only the negative gave the correct answer :frown: