persamaan garis lurus melalui titik P(-2,3) dan tegak lurus garis 4×-7y=28

y-y1=m(x-x1)
y-3=(-7/4)(x+2)
4y-12=-7x-14
4y=-7x-2

m₁ = - a/b = -4 / -7 = 4/7

karena yang ditanya tegak lurus, berlaku :
m₁ × m₂ = -1
4/7 × - 7/4 = -1 , maka m₂ = - 7/4

y - y₁ = m ( x - x₁ )
y - 3 = - 7/4 ( x + 2 )
y - 3 = - 7/4 x - 14/4
——————————— ×4
4(y-3) = -7x - 14
4y - 12 = -7x - 14
4y + 7x = -14 + 12
4y + 7x = -2 ........... (1)
4y + 7x + 2 = 0 ..... (2)
4y = -7x - 2 ........... (3)
y = -7/4 x - 2/4 ..... (4)