Merge pull request #91 from Dick-Lane/master

Add "weight" to part (d) of solution.
Remove 5 from correct answers

The additive identity is (0,1), so there is a zero vector and item 5 should be removed from the list of incorrect answers.
Remove 6 from correct answers

(x,y)+(-x,0) = (0,1), so additive inverses exist.
Update Proof_02.pg
Set domain to [-0.9,0.9]
Go from parserImplicitPlane to parserAssignment
Go from parserImplicitPlane to parserAssignment
Go from parserImplicitPlane to parserAssignment
Go from parserImplicitPlane to parserAssignment
Fix bug 3194
Fix bug 3195
Fixed instructions.
Fix bug 3196
Removed problem title
Fix domain
Putting math in math mode
Update to use number_list_cmp instead of asking for the averages of the values.
Merge remote-tracking branch 'upstream/master'
Set domain of x to [0.5,3]
Set domain of v and w to [0.5,4]