Question

While solving a question, I came with this term.

[a+(b-c)][a-(b-c)]
=(a+b-c)(a-b+c)
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How can (b-c) became (b+c) or positive in the second term.

Answer 1

WHEN -- IS MULTIPLIED TO ANY BRACKET THE WHOLE NUMERALS INSIDE THE BRACKET CHANGE...

Answer 2

It's because there is negetive sign before the bracket (b-c) in [a-(b-c)];

whenever there is a -ve sign before bracket the signs inside the bracket changes.