Answer:
a) [tex]f(x) = x + 3[/tex]
b) [tex]f(x) = -x - 5[/tex]
c) [tex]f(x) = 2x + 6[/tex]
Step-by-step explanation:
To determine the equation of a straight line, we need two things:
1. two known points (coordinates) on the line, used to calculate the gradient
2. the y-intercept of the line (the y-coordinate of the point at which the line crosses the y-axis)
Then we can use the equation:
[tex]\boxed {f(x) = ax + q}[/tex]
where a is the gradient and q is the y-intercept, to determine the equation of the line.
a) known points: (0, 3), (-4, -1)
y-intercept: 3
gradient = [tex]\frac{y_2 - y_1}{x_2 - x_1}[/tex]
⇒ [tex]\frac{3 - (-1)}{0 - (-4)}[/tex]
⇒ [tex]\bf 1[/tex]
∴ a = 1 , q = 3
∴ equation:
[tex]{f(x) = ax + q}[/tex]
[tex]f(x) = 1x + 3[/tex]
⇒ [tex]\bf f(x) = x + 3[/tex]
b) known points: (-7, 2) , (0, -5)
y-intercept = -5
gradient = [tex]\frac{2 - (-5)}{-7 - 0}[/tex]
⇒ [tex]\bf -1[/tex]
∴ equation:
[tex]f(x) = -1x + (-5)[/tex]
⇒ [tex]\bf f(x) = -x - 5[/tex]
c) known points: (-3, 0), (0, 6)
y-intercept = 6
gradient = [tex]\frac{6 - 0}{0 - (-3)}[/tex]
⇒ [tex]\bf 2[/tex]
∴ equation:
[tex]\bf f(x) = 2x + 6[/tex]
