a) \(\left(a+b+c\right)^2\)
\(=\left(a+b+c\right)\left(a+b+c\right)\)
\(=a\left(a+b+c\right)+b\left(a+b+c\right)+c\left(a+b+c\right)\)
\(=a^2+ab+ac+ba+b^2+bc+ca+cb+c^2\)
\(=a^2+b^2+c^2+\left(ab+ba\right)+\left(ac+ca\right)+\left(bc+cb\right)\)
\(=a^2+b^2+c^2+2ab+2ac+2bc\)
b,c,d tương tự nhs b!
1.
a) \(\left(a+b+c\right)^2=\left[\left(a+b\right)+c\right]^2\)
\(=\left(a+b\right)^2+2\left(a+b\right)c+c^2\)
\(=a^2+b^2+c^2+2ab+2bc+2ac\)
b)\(\left(a+b-c\right)^2=\left[\left(a+b\right)-c\right]^2\)
\(=\left(a+b\right)^2-2\left(a+b\right)c+c^2\)
\(=a^2+b^2+c^2+2ab-2ac-2bc\)
c)\(\left(a-b+c\right)^2=\left[\left(a-b\right)+c\right]^2\)
\(=\left(a-b\right)^2+2\left(a-b\right)c+c^2\)
\(a^2+b^2+c^2+2ac+2bc-2ab\)
d)\(\left(a-b-c\right)^2=\left[a-\left(b+c\right)\right]^2\)
\(=a^2-2a\left(b+c\right)+\left(b+c\right)^2\)
\(=a^2+b^2+c^2-2ab-2ac+2bc\)
nhớ tik mik nha
Mk chỉ gõ đáp án thôi nhé!
a) \(a^2+b^2+c^2+2ab+2bc+2ac\)
b)\(a^2+b^2+c^2+2ab-2bc-2ac\)
c) \(a^2+b^2+c^2-2ab-2bc+2ac\)
d) \(a^2+b^2+c^2-2ab+2bc-2ac\)
Hi Hi
