Question

how does this happen please explain me

a^2 + b^2 = ( a + b )^2 - 2ab ?how??​

Answer 1

Answer:

$(a + b)^{2} = {a}^{2} + {b}^{2} + 2ab \\ (a + b)^{2} - 2ab = {a}^{2} + {b}^{2} + 2ab - 2ab \\ (a + b)^{2} - 2ab = {a}^{2} + {b}^{2} \:$

As we know the formula above

Just subtract 2ab both sides

so that the 2ab on the right hand side of the equation

will be 0

And the final equation will be that one in the question