Vì f(x) chia hết cho x+3 nên ta có thể viết \(f\left(x\right)=2x^3-5x^2+x-a=\left(x+3\right).Q\left(x\right)\Rightarrow f\left(-3\right)=-102-a=0\Rightarrow a=-102\)

2A=2+2²+2³+2⁴+...+2³⁰

2A-A=2³⁰-1

suy ra: A=2³⁰-1 

suy ra A=B

\(15^2=\left(x^2+y^2\right)^2=x^4+y^4+2x^2y^2=x^4+y^4+2.6^2\Rightarrow x^4+y^4=15^2-2.6^2=153\)