Because a system of two linear equations has an infinite number of solutions, these lines must have the same slope and y-intercept. Option D is correct.
The slope of the line is described as the tangent angle of inclination of the line horizontally. i.e. m =tanx where x in degrees.
Both lines are parallel their slopes are the same. Both equations can now represent the same. The equations represent the same line, they are coincident and have an endless number of solutions.
Thus, A system of two linear equations has infinitely many solutions so these lines must have the same slope and equal y-intercept.
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