Riko wants to find the distance between the points [tex]$(-2, -3)$[/tex] and [tex]$(2, -5)$[/tex]. His work is shown below:

[tex]\[ |-3| + |-5| = 3 + 5 = 8 \][/tex]

Is Riko correct? Explain why or why not.



Answer :

Let's analyze Riko's method and then find the correct distance using the appropriate formula.

Riko calculated the distance by adding the absolute values of the y-coordinates:
[tex]\[ |-3| + |-5| = 3 + 5 = 8 \][/tex]

Riko's method is incorrect. He mistakenly added the absolute values of the y-coordinates, which does not give the correct distance between two points. Instead, the distance between two points [tex]\((x_1, y_1)\)[/tex] and [tex]\((x_2, y_2)\)[/tex] in the coordinate plane should be calculated using the distance formula:

[tex]\[ \text{Distance} = \sqrt{(x_2 - x_1)^2 + (y_2 - y_1)^2} \][/tex]

Let’s apply the distance formula to the points [tex]\((-2, -3)\)[/tex] and [tex]\((2, -5)\)[/tex]:

1. Calculate the difference in the x-coordinates:
[tex]\[ x_2 - x_1 = 2 - (-2) = 2 + 2 = 4 \][/tex]

2. Calculate the difference in the y-coordinates:
[tex]\[ y_2 - y_1 = -5 - (-3) = -5 + 3 = -2 \][/tex]

3. Square these differences:
[tex]\[ (x_2 - x_1)^2 = 4^2 = 16 \][/tex]
[tex]\[ (y_2 - y_1)^2 = (-2)^2 = 4 \][/tex]

4. Add the squares of the differences:
[tex]\[ (x_2 - x_1)^2 + (y_2 - y_1)^2 = 16 + 4 = 20 \][/tex]

5. Take the square root of the sum:
[tex]\[ \text{Distance} = \sqrt{20} = \sqrt{4 \cdot 5} = 2\sqrt{5} \approx 4.472 \][/tex]

Thus, the correct distance between the points (-2, -3) and (2, -5) is approximately [tex]\(4.472\)[/tex] units.

In conclusion, Riko is incorrect because he did not use the distance formula. He added the absolute values of the y-coordinates instead of calculating the actual Euclidean distance. The correct distance is approximately [tex]\(4.472\)[/tex] units.

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