What is the student error if a student rewrote $4 (9 x + 10)$ $4(9x + 10)$ as $36 x + 10$ $36x + 10$ ?

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Answer 1 · 2018-04-21T18:38:23

$36 x + 40$ $36x +40$

The student did not apply the distributive law correctly.

The $4$ $4$ in front of the bracket must be multiplied by both terms inside the bracket, not just the first as has been been done.

$4 (9 x + 10)$ $4(9x+10)$

$= 4 \times 9 x + 4 \times 10$ $= 4xx9x" " +" "4xx10$

$= 36 x + 40$ $=36x +40$

These are now unlike terms ans cannot be added.
The expressions is now simplified.

What is the student error if a student rewrote 4(9x+10)4(9x + 10) as 36x+1036x + 10 ?