x+1=9x^3 + 9x^2 solve the polynomial equation.
Been working on this one for awhile and i cant seem to get this one. 4 answers it needs.
No, it only needs 3 "answers", "solutions" or "roots", whichever
label you wish to give them. That's because the degree (largest
exponent of x) is 3.
Get zero on the right:
Multiply through by -1 so leading coefficient will be
positive:
Possible rational zeros are
±1, ±
, and ±
By DesCartes' rule of signs, there is one positive
answer (solution or root), and 2 or 0 negative ones.
Let's try x=1, that is, divide by x-1 to see if
1 is a solution:
1 | 9 9 -1 -1
| 9 -18 -19
----------------
9 -18 -19 -20
Nope, the remainder is -20, not zero, so x-1 is not a
divisor of
, and so x=1 is not
a solution.
Let's try x=-1, that is, divide by x+1 to see if
-1 is a solution:
-1 | 9 9 -1 -1
| -9 0 1
--------------
9 0 -1 0
Aha! The remainder is zero, so x+1 is a divisor of
of
, and therefore x=-1 is a
solution.
Anytime we divide by synthetic division and get a zero
remainder, we have factored the polynomial. In this
case we have factored
and now
we have
or eliminating the
term:
Now we can factor the expression in the second parentheses
as the difference of two perfect squares and get:
Setting each factor = 0,
x+1=0 gives x=-1
3x-1=0 gives x=
3x+1=0 gives x=
Edwin