Math Problem Statement

Garis k tegaklurus garis g dan saling berpotongan di titik (0, -12). Koordinat titik potong garis k dengan sumbu-x adalah …. A. (-6, 0), B. (-9, 0), C. (-12, 0), D. (-15, 0)

Solution

We are given a line gg in the Cartesian coordinate plane, where it intersects the x-axis at (16,0)(16, 0) and the y-axis at (0,12)(0, -12). Another line, kk, is perpendicular to line gg and intersects line gg at the point (0,12)(0, -12). We are tasked with finding the x-intercept of line kk, which means we need to find the point where line kk crosses the x-axis.

Step 1: Find the slope of line gg

The slope mm of a line is given by: m=y2y1x2x1m = \frac{y_2 - y_1}{x_2 - x_1} For line gg, we know the coordinates of two points: (0,12)(0, -12) and (16,0)(16, 0). So, the slope of gg is: mg=0(12)160=1216=34m_g = \frac{0 - (-12)}{16 - 0} = \frac{12}{16} = \frac{3}{4}

Step 2: Determine the slope of line kk

Since line kk is perpendicular to line gg, its slope will be the negative reciprocal of the slope of line gg. The slope of gg is 34\frac{3}{4}, so the slope of kk is: mk=43m_k = -\frac{4}{3}

Step 3: Find the equation of line kk

The general form of a line is: y=mx+cy = mx + c We know the slope of line kk is 43-\frac{4}{3}, and it passes through the point (0,12)(0, -12). Substituting into the equation: 12=43(0)+c-12 = -\frac{4}{3}(0) + c This gives c=12c = -12. Therefore, the equation of line kk is: y=43x12y = -\frac{4}{3}x - 12

Step 4: Find the x-intercept of line kk

The x-intercept occurs when y=0y = 0. Substituting y=0y = 0 into the equation of line kk: 0=43x120 = -\frac{4}{3}x - 12 Solve for xx: 43x=12\frac{4}{3}x = -12 Multiply both sides by 34\frac{3}{4}: x=12×34=9x = -12 \times \frac{3}{4} = -9

Thus, the x-intercept of line kk is (9,0)(-9, 0).

Answer:

The correct answer is B. (-9, 0).

Would you like more details or have any further questions?

Here are 5 related questions for further practice:

  1. How would the equation of line gg change if its slope were altered?
  2. What would happen if line kk intersected line gg at a different point?
  3. Can you determine the y-intercept of line gg directly from the diagram?
  4. How do perpendicular lines behave geometrically in other types of coordinate systems?
  5. What method would you use to find the point of intersection of two lines algebraically?

Tip: When working with perpendicular lines, always remember that their slopes are negative reciprocals of each other.

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Math Problem Analysis

Mathematical Concepts

Coordinate Geometry
Slopes of Perpendicular Lines
Equation of a Line

Formulas

Slope of a line: m = (y2 - y1) / (x2 - x1)
Equation of a line: y = mx + c
Slopes of perpendicular lines: m1 * m2 = -1

Theorems

Slopes of perpendicular lines are negative reciprocals

Suitable Grade Level

Grades 9-12