Question

Can someone explain the right answer? The question and answer is below.

Answer 1

Answer:

• x -3
• y +4
• Pythagorean theorem

Step-by-step explanation:

You want to find the horizontal and vertical distances between two points, and you want to know how to use those to find the distance between those points.

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horizontal distance

The x-coordinate of a point is its horizontal distance from the y-axis. The horizontal distance between two points will be the difference of their x-coordinates.

If the points are (3, -4) and (x, y), the x-coordinates are 3 and x. The difference between those coordinates can be written as x-3. (Usually, we subtract the first point from the second one.)

The horizontal distance from (3, -4) to (x, y) is (x -3).

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vertical distance

In like fashion, the y-coordinate of a point is its vertical distance from the x-axis. The vertical distance between two points will be the difference of their y-coordinates.

For the points (3, -4) and (x, y), the y-coordinates are -4 and y. The difference between those coordinates is y -(-4) = y +4.

The vertical distance from (3, -4) to (x, y) is (y +4).

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total distance

As the attachment shows, the horizontal and vertical distances between the two points can be considered to be the legs of a right triangle. The "total" distance between the points is the straight-line distance. It is the hypotenuse of that triangle.

The Pythagorean theorem gives the relation between the sides and hypotenuse of a right triangle. In this context, the Pythagorean theorem can be used to create an equation showing the relationship between the legs of the triangle and the distance from (x, y) to the center. (That distance is the radius.)

In particular, the equation created is ...

  (x -3)² +(y +4)² = 7²

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Additional comment

For right triangle legs 'a' and 'b', and hypotenuse 'c', the Pythagorean theorem tells you ...

  a² +b² = c²

The sum of the squares of the sides is equal to the square of the hypotenuse.