# equation of st.line

find equations:

1a)passing through (2,4)and with slope =3.

b)passing through (-2,3)and(3,1)

c)passing through(5,7)and with inclination 45。(angle)

2)Two points A(2,0) and B(4,4)are given.Find the mid-point of AB.

3)let L be a straight line joining A(2,5)andB(6,3).Find

a)the slope of L

b)the equation of L

c)the equation of the line perpendicular to L at A

4)find the coordinates:

a)L1:y=3x+2

L2:y=2x+1

thx a lot~

Extra(%):

a man bought an article for \$x.The article for sale at a marked price 70% higher than its cost.The article was then sold to a customer at a discount of 5%.

a)wt was the percentage gain for the merchant by selling the article?

b)if the customer paid \$2907 for the article,find the value of x.

### 1 個解答

• 最愛解答

1a) y - 4 = 3(x - 2)

3x - y - 2 = 0

1b) y - 1 = ((3-1)/(-2-3))(x - 3)

2x + 5y - 11 = 0

1c) y - 7 = (tan 45°)(x - 5)

x - y + 2 = 0

2) mid-pt. of AB = ( (2+4)/2 , (0+4)/2 )

........................= (3, 2)

3a)Slope of L = (5-3)/(2-6)

....................= -2/3

3b)equation of L

y - 5 = (-2/3)(x - 2)

2x + 3y - 19 = 0

3c) y - 5 = (3/2)(x - 2)

3x - 2y + 4 = 0

4a)L1:y=3x+2

L2:y=2x+1

3x + 2 = 2x + 1

x = -1

y = -2 + 1

y = -1

therefore (x , y) = ( -1, -1)