Question

Describe and correct the error in the solution.4d + 9d - (7 - 6d) = 4d + 9d - 7 - 6d= 4d + 9d - 6d - 7= 7d - 7

Answer 1

`\begin{gathered} 4d+9d-(7-6d)=4d+9d-7+6d \\ =4d+9d+6d-7 \\ =19d-7 \end{gathered}`

Explanation :

From the given expression :

`\begin{gathered} 4d+9d-(7-6d)=4d+9d-7-6d \\ =4d+9d-6d-7 \\ =7d-7 \end{gathered}`

The error is in the first line in the parenthesis.

It should be like this :

`-(7-6d)=-7+6d`

The sign of 6d must be positive because if you will distribute the negative sign outside the parenthesis to the negative sign inside the parenthesis, negative x negative = positive.

Since the first line is not correct, the succeeding lines is also not correct.

The corrected solution will be :

`\begin{gathered} 4d+9d-(7-6d)=4d+9d-7+6d \\ =4d+9d+6d-7 \\ =19d-7 \end{gathered}`