Question

Lisa wrote the expression (3x + 6x) - 2(x + 1) + 5. She simplified the expression using the following steps:

Step one: 3(1 + x) - 2(x + 1) + 5
Step two: 3(x + 1) - 2(x +1) + 5
Step three: (x + 1) + 5
Step four: x + 6
Lisa says that (3x + 6x) - 2(x + 1) + 5 = x + 6. Lisa's statement is incorrect. In which step did Lisa first make the mistake, and what is the correct expression for that step? Show your work.

Answer 1

Explanation:

Alright, lets get started.

The given expression is :
`(3x + 6x) - 2(x + 1) + 5`

In very first step, Lisa made a mistake.

Lisa took 3 as common factor out and what she wrote is 3 (1+x) but when she took 3 as common factor, the expression would be 3 (x+2x)

Here she made a mistake.

`3(x+2x)-2(x+1)+5`

`9x-2(x+1)+5`

`9x-2x-2+5`

`7x+3`

So, the correct answer is 7x+3 : Answer

Hope it willhelp :)

Answer 2

Step 1. Should be 3(x +2x) -2(x +1) +5 . . .

or . . . 3x(1 +2) -2(x +1) +5 . . .

or . . . 9x -2(x+1) +5

Explanation:

Lisa apparently failed to realize that both terms inside the first set of parentheses have 3x as a factor. They are like terms, so could be combined directly. If Lisa really wants to factor out 3 or 3x, she could do so and then combine the remaining factors at another step.