Help Please- Coordinate Geometry

Question:
The line x/a - y/b=4, where a and b are positive constants, meets the x-axis at M and the y-axis at N.
Given that the gradient of the line is 1/2 and that the length of MN is sqrt720 , find the values of a and b.

Help would be greatly appreciated,

Thanks

Question

Help Please- Coordinate Geometry 

Question:
The line x/a - y/b=4, where a and b are positive constants, meets the x-axis at M and the y-axis at N. 
Given that the gradient of the line is 1/2 and that the length of MN is sqrt720 , find the values of a and b. 

Help would be greatly appreciated, 

Thanks

anonymous · Answer

Here is the equation: |dw:1424755496177:dw|

triciaal · Answer

b x - a y =  4
 y =  b/a  x + 4 /a |dw:1424756205262:dw|


incomplete