(a-1)(a^2+a+1) - a^2(a-8) при a = 2\9

[latex](a-1)(a^2+a+1) - a^2(a-8)=a^3-1-a^3+8a^2=8a^2-1[/latex] [latex]a= \frac{2}{9} [/latex] [latex]8a^2-1=8*( \frac{2}{9} )^2-1=8* \frac{4}{81}-1= \frac{32}{81} -1=- \frac{49}{81} [/latex] [latex](a-b)(a^2+ab+b^2)=a^3-b^3[/latex]

Ответ: а^3-а^3+8а^2=-1+8а^2 при а=2/9 -1+8×2/9^2=-1+32/81=-81+32/81=-49/81