Question

840=2x²+2x.solve it​

Answer 1

two solutions are found :

1.20=x

2.-21=x

hence,

2x^2+2x=840

x=20

2(20)^2+2(20)=840

840=840

2x^2+2x=840

x=-21

2(-21)^2+2(-21)=840

840=840

hence 20,-21 are two solutions.