Question

in the given pair of linear equations 3x+ay=50 and 9x-21y=15 find thevalue of a for them to be a parallel

Answer 1

`3x + ay = 50\\ay = 50-3x\\ay = -3x + 50\\y =(-3x)/(a) + (50)/(a) \\\\slope = (-3)/(a) \\\\9x -21y = 15\\-21y = 15 -9x\\21y = 9x - 15\\\\y=(9x)/(21) - (15)/(21) \\\\Slope = (9)/(21) \\\\Since \ equations \ are \ parallel \ = m_(1) m_(2) = 1\\\\(-3)/(a) \cdot(9)/(21) = 1 \\\\(-27)/(21a) = 1\\\\\\(-9)/(7) = a`