Question

x^2+7=8x
x^2+18=9x
(-2x+1)(-2x-7)

Answer 1

$1); ; x^2+7=8x; ; to ; ; x^2-8x+7=0; ,\\x_1=1; ,; x_2=7; (teodrema; Vieta)\\2); ; x^2+18=9x; ; to ; ; x^2-9x+18=0; ,\\x_1=3; ,; x_2=6; ; (teorema; Vieta)\\3); ; (-2x+1)(-2x-7)=0\\4x^2+14x-2x-7=0; ; to ; ; 4x^2+12x-7=0\\D/4=6^2+4cdot 7=64; ,; ; x_1=frac{-6-8}{4}=-3,5; ;; ; x_2=frac{-6+8}{4}=0,5$