Question

Write an equation in standard form of the line passing through the points (3, 5) and (8, 15)
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Answer 1

hi,

a point is given ( x; y)

standar line equation is : y = ax+b

So with (3;5) and (8;15) we have :

3a+b = 5

8a+b = 15

so :

8a+b - ( 3a +b) = 15 -5

8a +b -3a -b = 10

8a-3a = 10

5a = 10

a = 10/5

a = 2

if a = 2 so 3*2 +b = 5

6+b = 5

b = 5-6

b = -1

so let check :

8*2 + (-1) = 16 -1 = 15

and 3*2 -1 = 6-1 = 5

coordonnate works for both point, so line is y = 2x -1