The x-coordinates of a point on t line joining the points `Q(2,2,1)a n dR(5,1,-2) is 4.` Find its z-coordinate.

Explanation

To find the z-coordinate of the point P on the line joining the points Q(2, 2, 1) and R(5, 1, -2) where the x-coordinate is given as 4, we can follow these steps:

### Step 1: Understand the problem
We have two points Q(2, 2, 1) and R(5, 1, -2). We need to find the coordinates of a point P on the line segment QR such that the x-coordinate of P is 4.

### Step 2: Set up the coordinates of point P
Let the coordinates of point P be (x, y, z). Since we know the x-coordinate is 4, we can write:
\[ x = 4 \]
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