56.a) \(\sqrt{7x^2}=x\sqrt{7}\)
b) \(\sqrt{8y^2}=2\sqrt{2y^2}\)
c) \(\sqrt{25x^3}=5x\sqrt{x}\)
d) \(\sqrt{48y^4}=4y^2\sqrt{3}\).
57.a) \(x\sqrt{5}=\sqrt{5x^2}\)
b) \(x\sqrt{13}=-\sqrt{13x^2}\)
c) \(x\sqrt{\dfrac{11}{x}}=\sqrt{\dfrac{11}{x}x^2}=\sqrt{11x}\)
d) \(x\sqrt{\dfrac{-29}{x}}=-\sqrt{\dfrac{-29}{x}x^2}=-\sqrt{-29x}\).