karleeahomer
contestada

please help I will give brainliest if two people answer my question
Which two equations would be most appropriately solved by using the quadratic formula? Select each correct answer. 0.25x2+0.8x−8=0
−(x−3)(x+9)=0
3x² = 9
−2x2+5x=7

Respuesta :

mathmate
0.25x2+0.8x−8=0  
same as 5x^2+16-160=0   no obvious factors for rational roots, so use quadratic formula
−(x−3)(x+9)=0   .... the factors are clearly (x-3) and (x+9), no need for formula
3x² = 9   ..... we see x^2=3, so roots are ± sqrt(3), no need for formula.
−2x2+5x=7 .... here b^2<4ac, definitely use quadratic formula.