(10x
2
+8x−5)−(−9x
2
−3x−4)
First, distribute the negative sign in front of the second polynomial:
(10x^2 + 8x - 5) + (9x^2 + 3x + 4)
Now, combine like terms:
10x^2 + 8x - 5 + 9x^2 + 3x + 4
= 19x^2 + 11x - 1
So, the final simplified expression is 19x^2 + 11x - 1.