[tex](a)\\ \\ \frac{2}{3}x^2+1=55 \\ \\\frac{2}{3}x^2=54 \\ \\ x^2=54\cdot \frac{3}{2} \\ \\ x^2= 81 \\ \\ x=б \sqrt{81} \\ \\ x_1=- 9\\ \\ x_2=9\\ \\ \\ (b) \\ \\ -2y^3-5=49 \\ -2y^3=49+5 \\-2y^3=54\\y^3= \frac{54}{-2} \\ y^3=- 27 \\ y^3= (-3)^3 \\ y=-3[/tex]
