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a+b=81
a-b=b:4
a=?
b=?
o vreau algebric


Răspuns :

a+b=81
a-b=b÷4⇒4×(a-b)=b⇒4a-4b=b⇒4a=5b⇒a=5b/4
inlocuim in a+b=81⇒5b/4+b=81(aducem la acelasi numitor)
5b+4b=324
9b=324
b=36⇒a+36=81⇒a=45