Помогите с номером 85(3-4)

3) $4\sqrt{9*3b}-5\sqrt{16*3b}+ \frac{1}{4}\sqrt{16*4*3b}=4*3\sqrt{3b}-5*4\sqrt{3b}+ \frac{4*2}{4}\sqrt{3b}=\sqrt{3b}*(12-20+2)=-6\sqrt{3b}$

4) $7x\sqrt{7^{2}*x^{2}*y^{4}*xy}+3x^{2}y\sqrt{8^{2}*y^{2}*y}-5\sqrt{6^{2}*x^{4}*y^{4}*xy}=49x^{2}*y^{2}\sqrt{xy}+24x^{2}y^{2}\sqrt{y}-30x^{2}*y^{2}\sqrt{xy}=x^{2}y^{2}\sqrt{y}*(49\sqrt{x}+24-30\sqrt{x})=x^{2}y^{2}\sqrt{y}*(19\sqrt{x}+24)$