Question

[lê phương thảo]

1 . tính

a.(a+b+c)^2 - (a+b)-c^2

b. CM (ac+bd)^2+(ad-bc)^2 = (a^2b^2) . (c^2+d^2)

Answer 1

[Nguyễn Lê Phước Thịnh]

a: \(=a^2+b^2+c^2+2ab+2bc+2ac-a^2-2ab-b^2-c^2=2bc+2ac\)

b: \(VT=a^2c^2+b^2d^2+2abcd+a^2d^2-2abcd+b^2c^2\)

\(=c^2\left(a^2+b^2\right)+d^2\left(a^2+b^2\right)\)

\(=\left(a^2+b^2\right)\left(c^2+d^2\right)\)