To find \( M + N \), we will add the two given polynomials \( M \) and \( N \).
Given: \[ M = 5x^{2} + 7x - 4 \] \[ N = -3x^{2} - 4x + 5 \]
Now, we will add \( M \) and \( N \):
\[ M + N = (5x^{2} + 7x - 4) + (-3x^{2} - 4x + 5) \]
Combining like terms:
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For \( x^{2} \) terms: \[ 5x^{2} - 3x^{2} = 2x^{2} \]
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For \( x \) terms: \[ 7x - 4x = 3x \]
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For constant terms: \[ -4 + 5 = 1 \]
Now, putting it all together: \[ M + N = 2x^{2} + 3x + 1 \]
Thus, the result is: \[ \boxed{2x^{2} + 3x + 1} \]