Question

x(x+1)(x+2)(x+3)=840

Answer 1

x(x+3)[(x+1)(x+2)=840
(x^2+3x)(x^2+3x+2)=840
put,x^2+3x=m
m(m+2)=840
(m-28)(m+30)
m=28 or m=-30
resubstituting,
x^2+3x-28=0
(x+7)(x-4)
x=-7 or x=4