Question

Which is an equation of the line with slope -3 and passes through (2,-1)?

A. y = 5x - 3
B. y = -3(x + 5)
C. 3x + y = 5
D. -3x + y = 5​

Answer 1

C. 3x + y = 5.

Explanation:

Using the point-slope form of the equation of a straight line:

y - y1 = m(x - x1) where m = the slope and (x1, y1) is a point on the line.

So substituting we have:

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

y + 1 = -3x + 6

y = -3x + 5

3x + y = 5.

Answer 2

C

Explanation:

The equation of a line in slope- intercept form is

y = mx + c ( m is the slope and c the y- intercept )

Here m = - 3, so

y = - 3x + c ← is the partial equation

T find c substitute (2, - 1) into the partial equation

- 1 = - 6 + c ⇒ c = - 1 + 6 = 5

y = - 3x + 5 ← in slope- intercept form

Add 3x to both sides

3x + y = 5 ← in standard form → C