Given: 2x2+5x−1+8x+x2+7−6x+3−3x2
On rearranging like terms together, we get,
⇒2x2+x2−3x2+5x+8x−6x−1+7+3
=(2+1−3)x2+(5+8−6)x+9
=0x2+7x+9
Hence, 2x2+5x−1+8x+x2+7−6x+3−3x2=7x+9