Answer:

Step-by-step explanation:
The distance formula is given by:

We are given the two points (4, -1) and (a, 5). The distance between them is 10.
Let (4, -1) be (x₁, y₁) and let (a, 5) be (x₂, y₂). Substitute:

Solve for <em>a</em>. Square both sides and simplify:

Simplify:

Take the square root of both sides. Since we are taking an even root, we will need plus/minus. Hence:

Solve for <em>a:</em>
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So, our two possible points are (12, 5) or (-4, 5).