Choose the main technique to prove the following statement:
3x+21=03x+21=0 has an integer solution.
Choose the main technique to prove the following statement:
x2+2x−8=0x^2 + 2x -8=0 has integer solutions.
Choose the main technique to prove the following statement.
√3\sqrt{3} is irrational.
Choose the main technique to prove the following statement.
If nn is even, then 5n2+6n+75n^2+6n+7 is odd.