algebra
posted by jason .
i need help with these kind of problems 3x(3x + 5)(10x+2)

Do the (3x+5)(10x+2) first and multiply by 3x later.
Do you know FOIL (first, outer, inner, last) ?
If so use it:
3x [ 3x*10x + 3x*2 + 5*10x + 5*2]
= 3x [ 30 x^2 + 56 x + 10 ]
If you do not know FOIL, use distributive property directly:
= 3x [ 3x(10x+2) + 5(10x+2) ]
= 3x [ 30 x^2 + 6x + 50x + 10 ]
= 3x [ 30 x^2 + 56 x + 10 ] which we already knew from FOIL
now do the 3x times
= 90 x^3 + 168 x^2 + 30 x