How do you write an equation of a line given (-20,-10) and (5,15)?

2 Answers
Jun 20, 2018

(y- -10)(5 - -20) = (x - -20)(15 - -10)(y10)(520)=(x20)(1510)

25(y+10)=25(x+20)25(y+10)=25(x+20)

y=x+10y=x+10

Jun 20, 2018

Convert the equation into two-point slope form:
y-y_1=(y_2-y_1)/(x_2-x_1) (x-x_2)yy1=y2y1x2x1(xx2) .

The resulting equation being:
y+10=x-5y+10=x5

Explanation:

Let P_1P1 be (-20,-10)(20,10), with x_1=-20x1=20 and y_1=-10y1=10,
P_2P2 be (5,15)(5,15), with x_2=5x2=5 and y_2=15y2=15,

By substitution,

y-(-10)=(15-(-10))/(5-(-20)) (x-5)y(10)=15(10)5(20)(x5)

In evaluating,

y+10=25/25(x-5)y+10=2525(x5)

Further into:

y+10=x-5y+10=x5 which serves as the final answer.

Source: http://mathworld.wolfram.com/Two-PointForm.html