The point a is at –2 and the point b is at 7. marissa would like to divide this line segment in a 4: 3 ratio, and she would like to use the formula x = (x2 – x1) + x1.what values should she substitute into the formula?

The right formula is: [x - x₁] = (4 / 7) [x₂ - x₁]

And the values to substitute are:
x₂ = 7
x₁ = - 2

Explanation:

1) Use these variables:

x₂ = the x-coordinate of point B = 7
x₁ = the x-coordinate of point A = - 2
x = the x-coordinate of the point that divides the line segment AB in a 4:3 ratio.

2) State the lengths:

length x - x₁ = x - x₁
length x₂ - x₁ = x₂ - x₁

2) Set a proportion:
[x - x₁] / [x₂ - x₁] = 4 / 7

⇒ [x - x₁] = (4 / 7) [x₂ - x₁]

⇒ x = (4/7) [x₂ - x₁] + x₁

The values to substitute are:
x₂ = 7
x₁ = - 2
Which leads to:
⇒ x = (4/7) [7 - (-2)] + (-2) = (4/7)(9) - 2 = 36/7 - 2 = [36 - 14] / 7 = 22 / 7