Question

-9x⁴ + 8x² - 1= 0 решите тождество

Answer 1

Топ) 9x⁴+8x²-1=0  ⇒x²=y ⇒⇒9y²+8y-1=0 ;y₁=(-8+√64+4·9·1)/18=(-8+10)/18=1/9;
y₂=(-8-10)/18=-1;
x²=1/9;x₁=1/3;x₂=-1/3; x²≠-1