Posted by **Mike** on Thursday, March 29, 2012 at 4:21pm.

Points A and B are noted on the straight line y=2x+4.If the distance between them is 5,what is the difference between their y-coordinates?

- Math -
**Reiny**, Thursday, March 29, 2012 at 6:48pm
Consider a circle with centre A and B any point on the circle.

let A be (0,4) , the y-intercept of y = 2x+4

the B must be both on y = 2x+4 and the circle

the equation of the circle would be

x^2 + (y-4)^2 = 25

sub in y = 2x+4

x^2 + (2x+4 - 4)^2 = 25

x^2 + 4x^2 = 25

5x^2 = 25

x^2 = 5

x = ±√5

consider x = +√5

then y = 2√5 + 4

and the difference in the y's between A and B is

2√5+4 - 4 = 2√5

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