Step-5

Title: Angle bisector theorem

Grade: 7-a Lesson: S3-L1

Explanation:

Step Type Explanation Answer

1

Problem

Consider the triangle ABC, If BD is the angle bisector for angle B, determine the value of x?.

5

2

Given

ABC is a traingle and BD is the anglular bisector of \$\angle B\$,
and sides AB = 4, BC = 6, AD = x, and DC = x + 2.

3

Step

From the given \$\triangle ABC\$, according to the angle bisector theorem, we have

\begin{align} \require{cancel} && \frac{AB}{BC} &= \frac{AD}{DC} \\ \end{align}

4

Step

Substitute the values.

\begin{align} \Rightarrow && \frac{4}{6} &= \frac{x}{x + 2} \\ \end{align}

5

Step

Multiply.

\begin{align} \Rightarrow && 6x &= 4x + 8 \\ \end{align}

6

Step

Subtract like terms.

\begin{align} \Rightarrow && 2x &= 8 \\ \end{align}

7

Step

Cancel out common factor.

\begin{align} \Rightarrow && \cancel{2}^1 x &= \cancel{8}^4 \\ \end{align}

8

Step

Answer

The value of x = 4.


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