8x²+7x-4)-(5x²-4x-3)

To simplify the expression \((8x² + 7x - 4) - (5x² - 4x - 3)\), we can first distribute the negative sign across the second polynomial:

\[ 8x² + 7x - 4 - 5x² + 4x + 3 \]

Now, combine like terms:

1. Combine the \(x²\) terms: \[ 8x² - 5x² = 3x² \]

2. Combine the \(x\) terms: \[ 7x + 4x = 11x \]

3. Combine the constant terms: \[ -4 + 3 = -1 \]

Now, putting it all together, we get:

\[ 3x² + 11x - 1 \]

So, the simplified expression is:

\[ \boxed{3x² + 11x - 1} \]