Maths Straight Line

2015-01-14 6:36 am
1. In each of the following, find the equation of the straight line L satisfying:
(a) Passing through (0, 0) and with slope -4
(b) Passing through (3, -7) and with slope 0
(c) Passing through (4, 9) and perpendicular to the x-axis.

2. Find the equation of the straight line passing through (2, -5) and (-2, 1).

3. In each of the following, find the equation of the straight line L with the given
(a) y-intercept=4; m=7
(b) x-intercept=4; m=3

4. The vertices of Triangle ABC are A(3, 0), B(0, 2) and C respectively. C is a point on the y-axis and touches point A. If the slope of CA is twice that of BA, find
(a) the equations of BA and CA,
(b) the coordinates of C,
(c) the area of Triangle ABC

回答 (3)

2015-01-14 8:41 am
✔ 最佳答案
1.
(a)
y - 0 = (-4) (x - 0)
y = -4x
4x + y = 0

(b)
y - (-7) = (0) (x - 3)
y + 7 = 0
y = -7

(c)
perpendicular to the x-axis means parallel to the y-axis.
This is a vertical line passing through (4, 9)
That is, x = 4.

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2.
Slope = [1 - (-5)]/(-2 - 2) = 6/(-4) = -3/2
Equation is:
y - 1 = (-3/2)[x - (-2)]

y - 1 = (-3/2)(x + 2)
2y - 2 = -3x - 6
3x + 2y + 4 = 0

✿ ❀ ✿ ❀ ✿ ❀ ✿ ❀ ✿ ❀ ✿ ❀ ✿ ❀ ✿ ❀ ✿ ❀ ✿ ❀ ✿ ❀ ✿ ❀ ✿ ❀ ✿ ❀ ✿ ❀

3.
(a)
y-intercept = 4, that is, passes through (0, 4)
y - 4 = 7(x - 0)
y - 4 = 7x
y = 7x + 4
7x - y + 4 = 0

(b)
x-intercept = 4, that is, passes through (4, 0)
y - 0 = 3(x - 4)
y = 3x - 12
3x - y - 12 = 0

✿ ❀ ✿ ❀ ✿ ❀ ✿ ❀ ✿ ❀ ✿ ❀ ✿ ❀ ✿ ❀ ✿ ❀ ✿ ❀ ✿ ❀ ✿ ❀ ✿ ❀ ✿ ❀ ✿ ❀

4.
(a)
Slope of BA = (2 - 0)/(0 - 3) = -2/3
Equation of BA is
y - 0 = (-2/3)(x - 3)
3y = -2x + 6
2x + 3y - 6 = 0

Slope of CA = 2 × (Slope of BA) = 2 × (-2/3) = -4/3
Equation of CA is
y - 0 = (-4/3)(x - 3)
3y = -4x + 12
4x + 3y - 12 = 0

(b)
Using (a), put x = 0 in 4x + 3y - 12 = 0 to get
0 + 3y - 12 = 0
y = 4
Therefore, C = (0, 4)

(c)
Regard BC as the base, BC = 4 - 2 = 2
The height of triangle ABC is 3, observed from the x-coordinate of A.
The area of triangle ABC is
(1/2)(2)(3) = 3 sq. units.
2015-04-20 6:08 pm
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