數學難題指教

1. (-2d)+(+5e)-9d
Ans : -2d+5e-9d => 5e-11d


2. 2x(-5g)-3x(+4g)
Ans : -10g-12g => -22g


3. Peter has p $5 coins and q $2 coins in his wallet,while Susan has p $1 coins and q $0.5 coins in her wallet.
(a) Express the amount each of them has in terms of p and q.
Ans : Peter has $5p+$2q
Susan has $1p+$0.5q
(b) Hence find the total amount they have in terms of p and q.
Ans : they have ($5p+$2q)+($1p+$0.5q) = $6p+$2.5q


4. 2009 2008 2007 3 2
Calculate ---------- x ---------- x --------- x ... x ----- x ----- .
2008 2007 2006 2 1
Briefly explain how you get the answer.
do not under the question


5.In a sale,the salling price of a refrigerator is $1150 less than the marked price .
If the discount percentage is 23%,find the selling price of the refrigerator.
Ans = $1150/23% = $5000

6.Given that the distance between A(-5,-2) and B(x,-2) is 6 units.Are the coordinaes of B unique? Briefly explain your answer.
Ans : No, the coordinates of B is not unique, as only Y-coordiate of B is fixed as (-2), then X-coordiate of B can be either (-11,-2) or (1,-2)

Hope it can help