Step-by-step explanation:
remember :
(a + b)² = (a + b)(a + b) = a² + 2ab + b²
similar
(a - b)² = (a - b)(a - b) = a² - 2ab + b²
let's compare this to the given expression :
d² - 10d + 25
so,
a = d
b = 5
(d - 5)² = d² - 2×5d + 5² = d² - 10d + 25
it is identical.
the factorization is therefore
(d - 5)(d - 5)
FYI
and don't forget either :
(a + b)(a - b) = a² - b²
