Question

10x - 25 - x²

(a+b)³ + (a-b)³

Answer 1

\(a.10x-25-x^2=-\left(x-5\right)^2\\ b.\left(a+b\right)^3+\left(a-b\right)^3=\left(a+b+a-b\right)\left[\left(a+b\right)^2-\left(a+b\right)\left(a-b\right)+\left(a-b\right)^2\right]\\ =2a.\left(a^2+2ab+b^2-a^2+b^2+a^2-2ab+b^2\right)=2a.\left(a^2+3b^2\right)\)

Answer 2

Ta có 10x-25-x^2

=-(x^2-10x+5^2)

=-(x-5)^2

Ta có (a+b)^3+(a-b)^3

=a^3+3a^2b+3ab^2+b^3+a^3-3a^2b+3ab^2-b^3

=2a^3+6ab^2-b^3

Answer 3

\(10x-25-x^2=-\left(x^2-10x+25\right)=-\left(x-5\right)^2\)

\(\left(a+b\right)^3+\left(a-b\right)^3=a^3+3a^2b+3ab^2+b^3+a^3-3a^2b+3ab^2-b^3=2a^3+6ab^2\)