Math Problem Statement

Suku pertama dan suku ketiga suatu deret geometri positif adalah 9 dan 1. Jumlah lima suku pertama deret tersebut adalah ...

Solution

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Question 11:

The first and third terms of a geometric series are 9 and 1. The sum of the first five terms is...

Let the first term be aa and the common ratio be rr. The general form of a geometric sequence is: a,ar,ar2,ar3,a, ar, ar^2, ar^3, \dots Given that the first term a=9a = 9 and the third term ar2=1ar^2 = 1, we can find rr: 9r2=1r2=19r=139r^2 = 1 \quad \Rightarrow \quad r^2 = \frac{1}{9} \quad \Rightarrow \quad r = \frac{1}{3}

Now, we can use the sum formula for a geometric series: Sn=a1rn1rS_n = a \frac{1 - r^n}{1 - r} For the first five terms: S5=91(13)5113=91124323=9×242243×32=3267243=13.45S_5 = 9 \frac{1 - \left( \frac{1}{3} \right)^5}{1 - \frac{1}{3}} = 9 \frac{1 - \frac{1}{243}}{\frac{2}{3}} = 9 \times \frac{242}{243} \times \frac{3}{2} = \frac{3267}{243} = 13.45

So, the closest answer is (A) 134913 \frac{4}{9}.


Question 12:

The diagram shows an isosceles trapezoid ABCD. The coordinates of point CC are asked in terms of pp and qq, where the value of p+2qp + 2q is sought.

For this question, you would typically need more details, like a clearer view of the trapezoid and any related points or coordinates.


Question 13:

The graph represents a line kk, and you are asked to find g(10)g(10), where the line represents the function gg.

The line crosses the x-axis at x=0x = 0 and appears to have a negative slope. The exact equation of the line would depend on its slope and intercepts, but without clear markings on the graph, it's hard to give an exact answer. If additional information is provided, such as the slope or intercepts, we could calculate g(10)g(10).


Question 14:

Calculate the shaded area in the diagram.

The diagram shows a shaded parallelogram on a grid. The formula for the area of a parallelogram is: Area=base×height\text{Area} = \text{base} \times \text{height} From the grid, the base and height can be visually estimated. The closest area value appears to be (B) 8.


Question 15:

Identify the coordinates on the line kk.

You are asked to find which of the given coordinates lies on line kk. By inspecting the graph, it's likely that the point is (B) (-1, 5), though verifying this requires knowing the equation of the line.


Would you like further explanations or details on any specific part? Here are some follow-up questions:

  1. How do we determine the common ratio in a geometric progression from two terms?
  2. What is the sum formula for a geometric series, and how is it applied to different values of nn?
  3. How can the coordinates of a point in a trapezoid be determined using geometric properties?
  4. How do you calculate the area of a parallelogram when given base and height?
  5. What is the method for determining the equation of a line from a graph?

Tip: In geometric series, finding the ratio between terms helps quickly solve for unknowns like the sum or a specific term in the series.

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Math Problem Analysis

Mathematical Concepts

Geometric Progression
Sequences
Summation of Series

Formulas

Sum of geometric series: S_n = a(1 - r^n) / (1 - r)

Theorems

Geometric Series Summation Formula

Suitable Grade Level

Grades 10-12