\(\frac{a}{b}=\frac{2}{3}=>\frac{a}{2}=\frac{b}{3}\)
Ta có:
\(\frac{a}{2}=\frac{b}{3}=\frac{a^3-b^3}{2^3-3^3}=\frac{19}{-19}=-1\)
Dó đó a = -1 . 2 = -2
b = -1 . 3 = -3
a/b=2/3=>a/2=b/3
Đặt a/2=b/3=k=>a=2k;b=3k
=>a^3-b^3=(2k)^2-(3k)^3=4.k^3-9.k^3=19
=>k^3.(4-9)=19=>k^3.-5=19
=>k^3=19/-5=...( sai đề ak)
Ta co : a/b=2/3=>a/2=b/3=>a^3/8=b^3/27
Ap dung tinh chat day ti so bang nhau :
a^3/8=b^3/27=a^3-b^3/8-27=19/-19=-1
Suy ra :a^3/8=-1=>a^3=-1.8=-8=>a=-2
b^3/27=-1=>b^3=-1.27=-27=>b=-3
=> a=-2 và b=-3
Vay a+b=-2+-3=-5
