Poster=6$
Frame=15$
9p+15f=X
9(6)+15(6)=X
54+90=X
X=144
Total cost is 144$
The answer would be -8+-88a
<span>P = (6,31°) is already a polar coordinate.
In the notation (r, </span>α) if you make r negative, it points in the opposite direction. If you add 180° to α you compensate for that.
Therefore (6,31°) = (-6,31°+180°) = (-6, 211°)
However, it is more usual to keep r positive.
