Consider the complete question is "The equation of the line [tex]L_1[/tex] is y=5x+1 and the equation of line [tex]L_2[/tex] is 2y-10x+3=0. How can you show that these two lines are parallel?"
Given:
Equation of [tex]L_1[/tex] is [tex]y=5x+1[/tex].
Equation of [tex]L_2[/tex] is [tex]2y-10x+3=0[/tex].
To show:
The these line as parallel.
Solution:
We have,
[tex]y=5x+1[/tex] ...(i)
[tex]2y-10x+3=0[/tex] ...(ii)
Equation (ii) can be written as
[tex]2y=10x-3[/tex]
[tex]y=\dfrac{10x-3}{2}[/tex]
[tex]y=\dfrac{10x}{2}-\dfrac{3}{2}[/tex]
[tex]y=5x-\dfrac{3}{2}[/tex] ...(iii)
Slope intercept form of a line is
[tex]y=mx+b[/tex] ...(iv)
where, m is slope and b is y-intercept.
On comparing (i) with (iv), we get slope of line [tex]L_1[/tex].
[tex]m_1=5[/tex]
On comparing (iii) with (iv), we get slope of line [tex]L_2[/tex].
[tex]m_2=5[/tex]
Since, [tex]m_1=m_2[/tex], therefore, lines [tex]L_1[/tex] and [tex]L_2[/tex] and parallel because slope of two parallel lines are always equal.
Hence proved.