Question

produsul a 2 numere este 420. marind un termen cu 5 si micsorand celalalt termen cu 2, produsul lor este 400

Answer 1

ab=420                         ab=420                         ab=420       
(a+5)(b-2)=400             ab+5b-2a-10=400         420+5b-2a=410

ab=420                       2ab=840                    (10+5b)b=840          
5b-2a=-10                   2a-5b=10                   2a=10+5b

5b²+10b-840=0
Δ=100+16800=16900
b1=(-10-130)/10=-14                  a1=(10-70)/2=-30
b2=(-10+130)/10=12                  a2=(10+60)/2=35

Raspuns: -30 si -14  sau     35 si 12