Question

Докажите тождество :
1)(a³+1)(a-1)=(a²-a+1)(a²-1)
2)m³+1=m(m+1)+(1-m)(1-m²)
3)( a+2)(a²-2a+4)-a(a-3)(3+a)=9a+8

Answer 1

$1)( {a}^{3} + 1)(a - 1) = (a + 1)( {a}^{2} - a + 1)(a - 1) = ( {a}^{2} - 1)( {a}^{2} - a + 1)$
$( {m}^{3} + 1) = (m + 1)(m + (1 - m) ^{2} ) = m(m + 1) + (1 - m)(1 - {m}^{2} )$
${(a - 2)}^{2} (a + 2) - ( {a}^{2} - 9)a = ( {a}^{2} - 4)(a - 2) - {a}^{3} + 9a = {a}^{3} - 2 {a}^{2} - 4a + 8 - {a}^{3} + 9a = 9a + 8 - 2 {a}^{2}$