Question

Cho a > b . Tính \(\left|S\right|\) biết

S = - ( a - b - c ) + ( -c + b + a ) - ( a + b )

Answer 1

\(S=-\left(a-b-c\right)+\left(-c+b+a\right)-\left(a+b\right)\\ S=-a+b+c-c+b+a-a-b\\ S=b-a\\ ta\:có\:a>b\Rightarrow\left|S\right|=a-b\)

Answer 2

a) a^2+b^2 = (a+b)^2 - 2ab
b) a^3+b^3 = (a+b)^3 - 3a.b(a+b)
c) a^4 +b^4 = (a^2 +b^2)^2 -2a^2.b^2 = [ (a+b)^2 -2ab)]^2 -2a^2.b^2
d) a^5 +b^5= (a^4 +b^4).(a+b) - ab(a^3+b^3)

Answer 3

S = - ( a - b - c ) + ( -c + b + a ) - ( a + b )

=> S= - a+ b+ c + -c + b+ a - a - b

=> S= (-a+ a) + ( b+ -b) + ( c+ -c) + ( b-a)

=> S= b-a

mà a> b

Nên | S| = a-b