52
- is prime? No
- is multiple of 3? No
continue
53
- is prime? Yes
continue
54
- is prime? No
- is multiple of 3? Yes
- is multiple of 4? No
continue
55
- is prime? No
- is multiple of 3? No
continue
56
- is prime? No
- is multiple of 3? No
continue
57
- is prime? No
- is multiple of 3? Yes
- is multiple of 4? No
continue
58
- is prime? No
- is multiple of 3? No
continue
59
- is prime? Yes
continue
60
- is prime? No
- is multiple of 3? Yes
- is multiple of 4? Yes
Therefore 60 is the answer, as it fits all the conditions
Simple trial and error.
For these kinds of expressions use FOIL (first, outside, inside, last).
-2x • 9x = -18x^2
-2x • -3y = 6xy
8y • 9x = 72 xy
8y • -3y = -24y^2
Now combine them all:
-18x^2 + 78xy - 24y^2
