Answer:
k = -10
Step-by-step explanation:
[tex]p(x)=3x^{4} - 9x^{3} + x^{2} + 15x + k\\3x^{2} (x^{2} -3x + y) -5 (x^{2} -3x + y)[/tex]
When we expand the above
[tex]p(x)=3x^{4} - 9x^{3} + 3x^{2}y- 5x^{2} + 15x - 5y[/tex]
When we take consider [tex]x^{2}[/tex] with the original expression
3y - 5 = 1
3y = 6 ⇒ y = 2
k = -5y ⇒ k = -10
