Question

Cine stie sa rezolve:
A+B=10
A×B=10
A=?

Answer 1

A+B=10 => A=10-B
AxB=10 => (10-B)xB=10 => 10B-B²=10 => B²-10B+10=0
Δ=100-40=60=(2√15)²
B1=(10+2√15)/2 => B1=5+√15 => A1=10-(5+√15) => A1=5-√15
B2=(10-2√15)/2 => B2=5-√15 => A2=10-(5-√15) => A2=5+√15

Deci A poate fi 5-√15 sau 5+√15