Question

(a + b -c+d)(a+b+c-d)​

Answer 1

Answer:

$= > (a + b - c + d)(a + b + c - d) \\ = > a {}^{2} + ab + ac - ad \\ + ab + b {}^{2} + bc - bd - ac - bc - c {}^{2} + cd \\ + ad + bd + cd - d {}^{2} \\ = > a {}^{2} + b {}^{2} - c {}^{2} - d {}^{2} + 2ab$