Question

he slope of the line that contains the points (1, -1) and (2, 3) is 4. What is the y-intercept? A. 5 B. 4 C. -4 D. -5

Answer 1

We know that:

• Given points: (1, -1) and (2, 3)
• Slope = 4

Picking any point:

• => (1, -1)

Using point slope form:

• y - y₁ = m(x - x₁)
• y - (-1) = 4(x - 1)
• y + 1 = 4x - 4
• y = 4x - 4 - 1
• y = 4x - 5

Comparing the equation with the formula:

• y = (m)x + (b) and y = (4)x + (-5)

⇒ m = slope = 4

⇒ b = y-intercept = -5

Answer 2

D

Explanation:

Equation of a line given by the two-point form is:

(y-y1)/(x-x1) = (y1-y2)/(x1-x2)

(y-(-1))/(x-1) = (-1-3) / (1-2)

(y+1)/(x-1) = -4 / -1

y+1 = 4(x-1)

y = 4x-4-1

y = 4x - 5

y-intercept at x=0 is -5

Answer is D.