A) daca a=7, b+c=15 si b-c=7,calculati ab+ac si ab-ac. b) daca a=7 si b+c+d-70, calculati ab+ac+ad. c) daca a=3 si b+c+d=30, calculati 3a+2 (ab+ac+ad). URGENT VA ROG... PLANG
(2) Răspunsuri
1. ab+ac=a(b+c)=7*15=105 si ab-ac=a(b-c)=7*7=49 2. ab+ac+ad=a(b+c+d)=7*70=490 3. 3a+2(ab+ac+ad)=9+2a(b+c+d)=9+6*30=9+180=189
ab+ac=ax(b+c)=7x15=105 => axb-axc=ax(b-c)=> 7x7=49
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