Question

chack whether 7+3x is a factor of 3x cube +7x

Answer 1

If it as factor then f(x) = 0
7 +3x = 0
3x = - 7
x = -7/3

Substituting -7/3 in 3x³ + 7x
3 (-7/3)³ + 7(-7/3) 
3(- 343/27) - 49/3
- 343/9 - 49/3
- ((343 + 49)/3)
- ((343 + 147)/9)
- (490/9)
- 54.4444
x = -7/3 is not satisfying the equation.
Therefore 7 + 3x is not a factor of this equation.