Question

Determinati x si y daca x+y=7radical din 3 si x•y=30

Answer 1

x+y=7√3 si x·y=30  

y=7√3-x

x(7√3-x)=30

7x√3-x²-30=0

sau x²-7x√3+30=0

Δ=147-120=27;  √27=3√3

x1=(7√3+3√3)/2=5√3=> y=7√3-5√3=2√3

x2=(7√3-3√3)/2=2√3=>y=5√3

x=5√3 si y=2√3

sau x=2√3 si y=5√3