(-6.4x+64)(x+28)=0
-6.4x^2-115.2x+1792=0 ÷-6.4
x^2+18x-280=0
a=1
b=18
c=-280
D=b^2-4ac=324+1120=144438
X1= -b-D/2a= -18-38/2= -56÷2= -28
X2= -b+D/2a= -18+38/2=20÷2=10
(-6.4x+64)(x+28)=0
-6.4x^2-115.2x+1792=0 ÷-6.4
x^2+18x-280=0
a=1
b=18
c=-280
D=b^2-4ac=324+1120=144438
X1= -b-D/2a= -18-38/2= -56÷2= -28
X2= -b+D/2a= -18+38/2=20÷2=10