tentukan persamaan garis a. melalui (2,3) dan bergradien -2 b. melalui (1,2) dan (4,-5) c. melalui (2,3) dan sejajar y=2x+5 d. melalui (1,-4) dan tegak lurus x

a) y - y1 = m ( x - X1 )
y - 3 = - 2 ( x - 1)
y = - 2x + 2 + 5
y + 2x = 7

b) ( y - y1) / ( y2 - y1 ) = ( x - X1 ) / ( x2 - X1 )
( y - 2) / ( - 5 - 2) = ( x - 1 ) / ( 4 - 1 )
( y - 2) / -7 = ( x - 1 ) / 3
3 ( y - 2) = - 7 ( x - 1)
3y - 6 = - 7x + 7
3y + 7x = 7 + 6
3y + 7x = 13

c) y = 2x + 5
m = 2
sejajar m1 = m2 = 2
y - y1 = m ( x - X1 )
y - 3 = 2 ( x - 2)
y = 2x - 4 + 3
y - 2x = - 1

d) x + 2y + 4 = 0
2y = - x - 4
m = - ½
tegak lurus
m1 . m2 = - 1
- ½ . m2 = - 1
m2 = 2
pers garis
y - y1 = m ( x - X1 )
y + 4 = 2 ( x - 1)
y = 2x - 2 - 2
y - 2x = - 4