SOLUTION: What is the value of k if point P(k, k square root 3 ) is 4 units from the line 5x+3y=12?

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Question 1094460: What is the value of k if point P(k, k square root 3 ) is 4 units from the line 5x+3y=12?

Answer by ikleyn(52813) About Me  (Show Source):
You can put this solution on YOUR website!
.
Thanks for re-posting in the plain text format.

There is a remarkable formula for the distance from the point (p,q) to the line ax + by + c = 0 in a coordinate plane.


This formula is


    d = abs%28a%2Ap+%2B+b%2Aq+%2B+c%29%2Fsqrt%28a%5E2%2Bb%5E2%29.


    (See the lesson The distance from a point to a straight line in a coordinate plane in this site).


In our case  p = k,  q = k%2Asqrt%283%29, a= 5, b= 3, c= -12.


So,  d = abs%285%2Ak+%2B+3%2Ak%2Asqrt%283%29+-+12%29%2Fsqrt%285%5E2+%2B+3%5E2%29 = abs%28%285%2B3%2Asqrt%283%29%29%2Ak+-+12%29%2Fsqrt%2834%29,


and your equation for the value of "k" is 


abs%28%285%2B3%2Asqrt%283%29%29%2Ak+-+12%29%2Fsqrt%2834%29 = 4.


Simplify it

abs%28%285%2B3%2Asqrt%283%29%29%2Ak+-+12%29 = 4%2Asqrt%2834%29.


There are TWO solutions for k:


1)  k = %2812+%2B+4%2Asqrt%2834%29%29%2F%285+%2B+s%2Asqrt%283%29%29,   and


2)  k = %2812+-+4%2Asqrt%2834%29%29%2F%285+%2B+s%2Asqrt%283%29%29.

Solved.

If you want to know how this formula was derived, look into the referred lesson.