Question

Пусть х*а=7, х+а=4, вычислите:
х^2-ха+а^2

Answer 1

$\left \{ {{x \cdot a=7} \atop {x+a=4}} \right. \\ \left \{ {{xa=7} \atop {x^2+2xa+a^2=16}} \right. \left \{ {{xa=7} \atop {x^2+a^2=2}} \right. \\ x^2+a^2-xa = 2 -7 = -5$