Đổi: \(71km/h=\dfrac{355}{18}m/s\)

\(v=a\cdot t\\ \Rightarrow\dfrac{355}{18}=a\cdot20\\ \Rightarrow a=\dfrac{71}{72}\left(m/s^2\right)\)

\(x+\dfrac{1}{2}x-25\%x=10\\ \Leftrightarrow x+\dfrac{1}{2}x-\dfrac{1}{4}x=10\\ \Leftrightarrow\dfrac{5}{4}x=10\\ \Leftrightarrow x=8\)

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

Vậy a = -2; b = 1.