Question

Function is a line points (3,2), (5,8), and (8,y) what is y

Answer 1

Y = mx + b

$(3;\ 2)\to x_1=3;\ y_1=2\\\\(5;\ 8)\to x_2=5;\ y_2=8\\\\m=\dfrac{y_2-y_1}{x_2-x_1}\to m=\dfrac{8-2}{5-3}=\dfrac{6}{2}=3$

Therefore we have: y = 3x + b.

Put the coordinates of the point (3; 2) to the equation of the line:

$2 = 3\cdot3+b\\2=9+b\ \ \ |-9\\b=-7$

Therefore we have: y = 3x - 7

Substitute the coordinates of the point (8; y) to the equation of the line:

$y = 3\cdot8-7=24-7=17$

Answer: y = 17.