Question 297347
Lines that are parallel have identical slopes. 
Both lines are in slope-intercept form, {{{y=mx+b}}}, where {{{m}}} is the slope. For both lines the slope is 2.
{{{ graph( 300, 300, -10,10,-10,10, 2x-5, 2x+5) }}}
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If the lines were perpendicular, then their slopes would be negative reciprocal of each other.
{{{m1*m2=-1}}}
Like {{{y=2x+5}}} and {{{y=-(1/2)x+5}}} as you see from the graph. 
{{{ graph( 300, 300, -10,10,-10,10, -(1/2)x+5, 2x+5) }}}
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If neither of those conditions held, then they would intersect at one point like
{{{y=2x+5}}} and {{{y=x-2}}}
{{{ graph( 300, 300, -10,10,-10,10, x+1, 2x+5) }}}