a + 5(a + 1) + (a + 5)(5a − 1) = a + 5a + 5 + 1(a + 5)(5a − 1) = a + 5a + 5 + (5a2 − a + 25a − 5) = a + 5a + 5 + 5a2 − a + 25a − 5 = 30a + 5a2
a + 5(a + 1) + (a + 5)(5a − 1) = a + 5a + 5 + 1(a + 5)(5a − 1) = a + 5a + 5 + (5a2 − a + 25a − 5) = a + 5a + 5 + 5a2 − a + 25a − 5 = 30a + 5a2