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The length of the line joining points (x,4) and (-x,3) is...

The length of the line joining points (x,4) and (-x,3) is 7 units. Find the value of x.

A.

4√3

B.

2√6

C.

3√2

D.

2√3

Correct answer is D

d = (x2x1)2+(y2y1)2
x1 = x, x2 = -x, y1 = 4, y2 = 3, d = 7
7 =  (xx)2+(34)2
7 = (2x)2+(1)2
7 = ( 4x2+1
square both sides
72 = 4x2 + 1
collect like terms
4x2 = 49 - 1
4x2 = 48

x2 = 484

x2 = 12
x = √12
x = 2√3