64m² - 96m + 36
note that factors of the form
(a - b)² = a² - 2ab + b²
for (8m - 6 ) with a = 8m and b = 6, then
(8m - 6)² = (8m)² - (2 × 8m × 6 ) + 6² = 64m² - 96m + 36
