Question

А) -20x=1.6x^2 б) 3x^2+7x-40=0 в) x^2-11x+30=0 г) x: x-1 -5: x+1 = 2: x^2-1

Answer 1

A) $-20x=1.6x^2$
$1.6x^2+20x=0$
$x(1.6x+20)=0$
$x1=0, x2= \frac{20}{1.6}$
$x2=12.5$
б) $3x^2+7x-40=0 ; D=7^2-4*3*(-40)=529$
$x1= \frac{-7+23}{2*3}= \frac{8}{3}$
$x2= \frac{-7-23}{2*3}= \frac{-10}{2}= -5$
в) $x^2-11x+30=0$
$D=11^2-4*30=1$
$x1= \frac{11+1}{2}=6$
$x2= \frac{11-1}{2}=5$
г) $\frac{x}{x} -1 - \frac{5}{x} +1 = \frac{2}{ x^{2} } -1?$