# Chapter 5 - Section 5.3 - Special Factoring - 5.3 Exercises: 26

$(5c-2+d)(5c-2-d)$

#### Work Step by Step

$\bf{\text{Solution Outline:}}$ To factor the given expression, $25c^2-20c+4-d^2 ,$ group the first $3$ terms since these form a perfect square trinomial. Then factor the trinomial. The resulting expression becomes a difference of $2$ squares. Factor this expression using the factoring of the difference of $2$ squares. $\bf{\text{Solution Details:}}$ Grouping the first $3$ terms above results to \begin{array}{l}\require{cancel} (25c^2-20c+4)-d^2 .\end{array} The trinomial above is a perfect square trinomial. Using $a^2\pm2ab+b^2=(a\pm b)^2,$ the expression above is equivalent to \begin{array}{l}\require{cancel} (5c-2)^2-d^2 .\end{array} The expression above is a difference of $2$ squares. Using $a^2-b^2=(a+b)(a-b),$ the factored form of the expression above is \begin{array}{l}\require{cancel} [(5c-2)+d][(5c-2)-d] \\\\= (5c-2+d)(5c-2-d) .\end{array}

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