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Given the point (-2, -9) divides the line segment joining (a, b) and (2, 7) in the ratio of 3:4, find the values of a and b.

Sagot :

Sure, let's solve this step-by-step.

We have a line segment joining two points [tex]\((a, b)\)[/tex] and [tex]\((2, 7)\)[/tex] that is divided by a point [tex]\((-2, -9)\)[/tex] in the ratio of 3:4.

To find the coordinates [tex]\((a, b)\)[/tex], we'll use the section formula for internal division of a line segment. The section formula states that if a point [tex]\((x, y)\)[/tex] divides the line segment joining [tex]\((x_1, y_1)\)[/tex] and [tex]\((x_2, y_2)\)[/tex] in the ratio [tex]\(m:n\)[/tex], then the coordinates [tex]\((x, y)\)[/tex] are given by:

[tex]\[ x = \frac{mx_2 + nx_1}{m + n} \][/tex]
[tex]\[ y = \frac{my_2 + ny_1}{m + n} \][/tex]

Given:
- The coordinates [tex]\((x_2, y_2) = (2, 7)\)[/tex]
- The coordinates [tex]\((x, y) = (-2, -9)\)[/tex]
- The ratio [tex]\(m:n = 3:4\)[/tex]

Let’s denote:
- [tex]\((x_1, y_1) = (a, b)\)[/tex]
- The point [tex]\((x, y) = (-2, -9)\)[/tex]

We will set up equations using the section formula and the given point [tex]\((-2, -9)\)[/tex]:

1. For the x-coordinate:
[tex]\[ -2 = \frac{3 \cdot 2 + 4 \cdot a}{3 + 4} \][/tex]

2. For the y-coordinate:
[tex]\[ -9 = \frac{3 \cdot 7 + 4 \cdot b}{3 + 4} \][/tex]

Now, let's solve these equations for [tex]\(a\)[/tex] and [tex]\(b\)[/tex].

Solving for [tex]\(a\)[/tex]:

[tex]\[ -2 = \frac{6 + 4a}{7} \][/tex]

Multiply both sides by 7:
[tex]\[ -14 = 6 + 4a \][/tex]

Subtract 6 from both sides:
[tex]\[ -20 = 4a \][/tex]

Divide by 4:
[tex]\[ a = -5 \][/tex]


Solving for [tex]\(b\)[/tex]:

[tex]\[ -9 = \frac{21 + 4b}{7} \][/tex]

Multiply both sides by 7:
[tex]\[ -63 = 21 + 4b \][/tex]

Subtract 21 from both sides:
[tex]\[ -84 = 4b \][/tex]

Divide by 4:
[tex]\[ b = -21 \][/tex]


So, the values of [tex]\(a\)[/tex] and [tex]\(b\)[/tex] are:
[tex]\[ a = -5 \][/tex]
[tex]\[ b = -21 \][/tex]

Thus, the coordinates [tex]\((a, b)\)[/tex] are [tex]\((-5, -21)\)[/tex].
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