101598:287 = 354

\(1-\frac12=\frac22-\frac12=\frac12\)

\(x^5+x^4+x^3+x^2+x+1\)

\(=\left(x^5+x^4+x^3\right)+\left(x^2+x+1\right)\)

\(=x^3\left(x^2+x+1\right)+\left(x^2+x+1\right)\)

\(=\left(x^3+1\right)\left(x^2+x+1\right)\)

\(=\left(x+1\right)\left(x^2-x+1\right)\left(x^2+x+1\right)\)

C

984

\(6:2\cdot\left(1+2\right)=6:2\cdot3=3\cdot3=9\)

\(x+2x+3x+4x+\cdots+2025x=2025\cdot2026\)

\(x\cdot\left(1+2+3+\ldots+2025\right)=2025\cdot2026\)

\(x\cdot\frac{2025\cdot\left(2025+1\right)}{2}=2025\cdot2026\)

\(x=2025\cdot2026:\frac{2025\cdot2026}{2}\)

\(x=2\)

x = 40 - 70

x = -30

\(2\cdot\left(\frac14-3x\right)=\frac15-4x\)

\(\frac12-6x=\frac15-4x\)

\(\frac12-6x-\frac15+4x=0\)

\(\frac{3}{10}-2x=0\)

\(\frac{3}{10}=2x\)

\(x=\frac{3}{20}\)

Vậy \(x=\frac{3}{20}\)

\(-1,6<-\frac{18}{12}<\frac{10}{-7}\)