(4.9+3.5x)(7x-2.8)=0 

(4.9 +3.5х)(7х -2.8)=0
4.9+3.5х=7х-2.8
3.5х-7х=-4.9-2.8
3.5х=7.7
х=7.7:3.5
х=2.2

34.3x+24.5x^-13.72-9.8x=0
24.5x^+24.5x-13.72=0
D=600.25+1344.56=1944.81
x1=  __-24.5 + 44.1__=0.4
                  49
x2=__-24.5-44.1__=-1.4
                 49