(r – 2)(s – 2)_____rs – 2r – 2s + 4______rs – 2(r + s) + 4

Product, or 

Sum, or 



rs – 2(r + s) + 4

7 – 2(19) + 4 -------- Substituting 7 for rs, and 19 for r + s



It's as simple as that! No complex calculations are necessary! 

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