On a number line, the directed line segment from [tex]\( Q \)[/tex] to [tex]\( S \)[/tex] has endpoints [tex]\( Q \)[/tex] at [tex]\(-8\)[/tex] and [tex]\( S \)[/tex] at [tex]\(12\)[/tex]. Point [tex]\( R \)[/tex] partitions the directed line segment from [tex]\( Q \)[/tex] to [tex]\( S \)[/tex] in a [tex]\( 4:1 \)[/tex] ratio.

Which expression correctly uses the formula [tex]\(\left(\frac{m}{m+n}\right)\left(x_2-x_1\right)+x_1\)[/tex] to find the location of point [tex]\( R \)[/tex]?

A. [tex]\(\left(\frac{1}{1+4}\right)(12-(-8))+(-8)\)[/tex]

B. [tex]\(\left(\frac{4}{4+1}\right)(12-(-8))+(-8)\)[/tex]

C. [tex]\(\left(\frac{4}{4+1}\right)(-8-12)+12\)[/tex]

D. [tex]\(\left(\frac{4}{1+4}\right)(-8-12)+12\)[/tex]



Answer :

Sure, let's solve this step by step.

### Given:
- Endpoint [tex]\(Q\)[/tex] at [tex]\(-8\)[/tex]
- Endpoint [tex]\(S\)[/tex] at [tex]\(12\)[/tex]
- Point [tex]\(R\)[/tex] partitions the segment [tex]\(QS\)[/tex] in a [tex]\(4:1\)[/tex] ratio

We're asked to find the expression that correctly uses the formula to locate point [tex]\(R\)[/tex]. The correct formula to use is:
[tex]\[ \left(\frac{m}{m+n}\right)\left(x_2-x_1\right)+x_1 \][/tex]
where:
- [tex]\(x_1\)[/tex] is the coordinate of point [tex]\(Q\)[/tex]
- [tex]\(x_2\)[/tex] is the coordinate of point [tex]\(S\)[/tex]
- [tex]\(m\)[/tex] and [tex]\(n\)[/tex] are the ratios in which [tex]\(R\)[/tex] partitions [tex]\(QS\)[/tex]

### Step-by-step Solution:
1. Identify the coordinates:
- [tex]\(x_1 = -8\)[/tex] (coordinate of [tex]\(Q\)[/tex])
- [tex]\(x_2 = 12\)[/tex] (coordinate of [tex]\(S\)[/tex])

2. Identify the ratio values:
- [tex]\(m = 4\)[/tex]
- [tex]\(n = 1\)[/tex]

3. Substitute the values into the formula:
[tex]\[ \left(\frac{4}{4+1}\right)\left(12 - (-8)\right) + (-8) \][/tex]

4. Simplify the expression inside the formula:
[tex]\[ \left(\frac{4}{5}\right)(12 + 8) - 8 \][/tex]

Thus, the correct expression is:
[tex]\[ \left(\frac{4}{4+1}\right)(12-(-8)) + (-8) \][/tex]

This matches the second option provided:
[tex]\[ \left(\frac{4}{4+1}\right)(12-(-8))+(-8) \][/tex]

Hence, the correct expression is:
\[
\left(\frac{4}{4+1}\right)(12-(-8))+(-8)
\