(1,3)(2,7)
slope = (7 - 3) / (2 - 1) = 4
y = mx + b
slope(m) = 4
use any of ur points (1,3)...x = 1 and y = 3
now we sub and find b, the y int
3 = 4(1) + b
3 = 4 + b
3 - 4 = b
-1 = b
so ur rule is : y = 4x - 1 or f(x) = 4x - 1
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(2,8)(3,11)
slope = (11 - 8) / (3 - 2) = 3
y = mx + b
slope(m) = 3
use any of ur points....(2,8)...x = 2 and y = 8
now sub and find b, ur y int
8 = 3(2) + b
8 = 6 + b
8 - 6 = b
2 = b
so ur rule is : y = 3x + 2 or f(x) = 3x + 2
