Question

.
$(9 - a)(9 + a) - (a - {9)}^{2}$
$(2 + x)(4 - 2x + {x}^{2} ) - ( {x}^{2} - 8)$
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Answer 1

(81-а2)-(а2-18)=81-18•а2=63a2
(2+x)(4-3х2)-(х2-8)=5х2