Saturday
August 23, 2014

Homework Help: Math

Posted by Jon on Saturday, April 25, 2009 at 3:43pm.

1.Find the distance between P(7, -4) and the line with equation x - 3y + 5 = 0 round to nearest tenth

3Y=x+5
y=(x+5)/3
-1/m
= -3
y=-3x+b
sub in P(7,-4)
-4=-3(7)+b
b=21-4
b=17
y=-3x+17
set the two equations equal.
-3x+17=(x+5)/3
-9x+51=x+5
46=10x
x=4.6
sub back in:
y= -3(4.6)+17= -13.8+17=3.2

distance=sqrt((7-4.6)^2+(-4-3.2)^2)
=sqrt((2.4)^2+(7.2)^2)
=sqrt(5.76+51.84)
=sqrt(57.6)=7.59
=7.6

Is there a shorter way to do this?

2.Write XY(with line over it) as the sum of unit vectors for X(8,2,-9) and Y(-12,-1,10).

There's an example just like this in my book but I really don't understand it.

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