Answer:
If you look over the steps you can see that until 4x + x + 3 = 18, evertything is dandy. But the step after that 4x + x =21 seems a bit fishy.
Think about it they subtract 3 from both sides so the first side is correct
4x + x, but they added 3 to the other side:
not
4x+x = 21
Then we solve for 4x + x = 15
To solve for y we use :
y = x+3
y = 3+3 = 6
so (3,6) is the right answer
To split this trinomial into two binomials, let's try and find two numbers which add to 6 and multiply to 8. To do this, we can list all the factors of 8 and then choose which factors also add to 6.
Factors of 8: (1, 8), (2, 4)
1 + 8 = 9, meaning that 1 and 8 are not the factors we are looking for. However, 2 and 4 do add to 6. By combining these numbers which an x (so that we can produce the term at the front of the trinomial), we find the binomials:
and
The answer is x + 2 and x + 4.