1) a) 9782+ 222+ 978.44 b) 8212 + 3212 - 821.642
= 9782 + 222 + 2. 22. 978 = 8212 + 3212- 2. 321 .821
= (978+22)2 = ( 821 - 321)2
= 10002 = 5002
= 1 000 000 = 250 000
2) (a+b+c)2+(a+b-c)2
= a2+b2+ c2 + 2ab +2ac+2bc+a2+b2-c2+ 2ab -2ac -2bc
= 2a2+2b2+4ab
= 2(a2 + b2 + 2ab)
= 2( a+b)2
\(\left(a+b+c\right)^2+\left(a+b-c\right)^2\)
\(=\left(a^2+b^2+c^2+2ab+2bc+2ca\right)+\left(a^2+b^2+c^2+2ab-2bc-2ca\right)\)
\(=a^2+b^2+c^2+2ab+2bc+2ca+a^2+b^2+c^2+2ab-2bc-2ca\)
\(=a^2+b^2+c^2+2ab+a^2+b^2+c^2+2ab\)
\(=2a^2+2b^2+2c^2+4ab\)
\(=2\left(a^2+b^2+c^2+2ab\right)\)
Cái kia mình làm có vẻ hơi tắt nhỉ (:
Làm từng cái một nè :
*\(\left(a+b+c\right)^2=\left[\left(a+b\right)+c\right]^2\)
\(=\left(a+b\right)^2+2\left(a+b\right)c+c^2\)
\(=a^2+2ab+b^2+2ac+2bc+c^2\)
\(=a^2+b^2+c^2+2ab+2bc+2ac\)
* \(\left(a+b-c\right)^2=\left[\left(a+b\right)-c\right]^2\)
\(=\left(a+b\right)^2-2\left(a+b\right)c+c^2\)
\(=a^2+2ab+b^2-2ac-2bc+c^2\)
\(=a^2+b^2+c^2+2ab-2bc-2ac\)
Ok rồi nhé =)
1. Phân tích các đa thức sau thành nhân tử:
