<h2>
Answer:</h2>

The solution for x in this equation is <em>18</em>.<em> </em>
Answer:
Step-by-step explanation:
-3x^4 -9x^3+ 15x^2
-3x^2 ( x^2 + 3x -5)
if you use quadratic formula (see image)
~~~~~~~~~~~~~~~~~~~~~~
10x^3 -35x^2 +6x -21
5x2(2x-7) +3(2x-7)
(5
+ 3) (2x-7)
Not sure about remainder theorem but I'm sure that the last terms should all multiply tho the last term
see the expanded form is -45
so the last terms of each binomial should multiply to -45
3 times -5 times ?=-45
-15 times ?=-45
divide by -15
?=3
the question mark is 3