Prove: if a^2-2a is even then a is even

Prove by contradiction

Step-by-step explanation:

If is even then is even

Prove by contradiction

is even then is odd

Also

Since is odd is also an odd number, the addition or subtraction of an even number with an odd number is an odd number.

The multiplication of two odd numbers yields to another odd number, then is odd but is equal to which is even, a number cannot be odd and even, this is a contradiction so must be even.

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step-by-step explanation: