Answer:
12x^2-4x
Step-by-step explanation:
5x + 4x^2 - 9x + 8x^2
Combine like terms
4x^2+8x^2+5x-9x
12x^2-4x
[tex]\begin{cases}\bf \large{\purple{ \implies}} \tt \: 5x \: + \: 4 {x}^{2} \: - \: 9x \: + \: 8 {x}^{2} \\ \\ \bf \large{\purple{ \implies}} \tt \: 4 {x}^{2} \: + \: 8 {x}^{2} \: + \: 5x \: - 9x \\ \\ \bf \large{\purple{ \implies}} \tt \: 12 {x}^{2} \: - \: 4x \end{cases}[/tex]
