Are the equation y = 3x + 7 and y = -3x + 7 parallel?
They are not parallel
They are not parallel, because their slopes are different, Slope of the first one is 3 and the slope of the second one is -3.
One is slope and the other way find the determinant of the matrix which should be zero for parallel lines
Write slope and intercept in matrix form
First row = (C11 C12) = (3 7)
Second row = (C 21 C22) = (-3 7)
Calculation of determinant for 2X2 matrix = C11C22 -(-C12C21)
i.e. (37- (-37) = 42 whic is not equal to zero
Hence these lines are not parallel