Step 1: Find the slopes of the two lines.
Given
\[
3x^2+5xy-4y^2=0.
\]
Put
\[
y=mx.
\]
Then
\[
3+5m-4m^2=0.
\]
Thus
\[
4m^2-5m-3=0.
\]
Solving,
\[
m=\frac{5\pm\sqrt{73}}{8}.
\]
These represent the two lines whose angle bisectors are required.
Step 2: Use the formula for angle bisectors of a pair of lines.
For a pair of lines
\[
ax^2+2hxy+by^2=0,
\]
the combined equation of the angle bisectors is obtained by rotating the axes to the bisector directions.
Applying the standard result to
\[
3x^2+5xy-4y^2=0,
\]
we obtain
\[
x^2-y^2-\frac{2}{5}xy=0.
\]
Step 3: Verify with the options.
Comparing with the given options, we find that option (1) matches exactly.
Step 4: Final conclusion.
Therefore, the equation of the angle bisectors is
\[
\boxed{x^2-y^2-\frac{2}{5}xy=0}.
\]