Answer
$(d-15)(d-3)$
Work Step by Step
To factor a trinomial in the form $d^2+bd+c$, we must find two numbers whose product is $c$ and whose sum is $b$. We then insert these two numbers into the blanks of the factors $(d+\_)(d+\_)$.
In the case of $d^2-18d+45$, we are looking for two numbers whose product is $45$ and whose sum is $-18$. The numbers $-15$ and $-3$ meet these criteria because: $$-15\times(-3)=45\;\text{and}\;-15+(-3)=-18$$When we insert these numbers into the blanks, we arrive at the factors: $(d-15)(d-3)$.
