Chưngs minh a²⁺b² >= (a+b)^2/2

|a|+|b|>=|a+b|

>= là lớn hơn hoặc bằng nha mn.nhan giúp mik vs ạ

cmr

2(a^3+b^3+c^3-3abc=(a+b+c)(a+b^2+(b-c)^2+(c-a)^2

(a+b)(b+c)(c+a)+4abc=c(a+b)^2+a(b+c)^2+b(c+a)^2

Rút gọn bt

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

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

Nhanh vs ạ

tìm lối sai

don't run so quick like that.you will stumble against a rock

my aunt has a five thousand stamps collection.she has collected them for 10 years

(a+b+c)^3-(a+b)^3-(a+c)^3-(b+c)^3 rút gọn biểu thức

f(x)=x^6-91x^5+91x^4-91x^3+91x^2-91x+91taij x=90

g(x)=1969-2021x+2021x^2-2021x^3+2021x^4-...+2021x^1968-x^1968 tại x=2020

nhanh vs ah