1)

х²(х+4) – 20х(х+4) + 100(х+4) =

= (х+4)(х² – 20х + 100) =

= (х+4)(х – 10)²

2)

а² – 36 – 2а(36 – а²) – а²(36 – а²) =

= (а² – 36) + 2а(а² – 36) + а²(а² – 36) =

= (а² – 36)(1 + 2а + а²) =

= (а² – 36)(1+а)²

3)

а²(b-1) –b²(a-1) =

= a²b – a² –ab² + b² =

= (a²b – ab²) -(a² – b²) =

= ab(a – b)– (a – b)(a+b) =

= (a – b)(ab– a – b)

4)

(m-n)(n³-p³)– (n-p)(m³ – n³) =

= (m - n)(n- p)(n²+ np + p²) – (n-p)(m – n)(m² + mn + n²) =

= (m - n)(n- p)((n²+ np + p²) –(m² + mn + n²)) =

= (m - n)(n- p)((n²+ np + p² –m² - mn - n²)