Determine the general solution of the differential equation y" =rcos 7r. I (Hint: Set v=y' and solve the resulting linear differential equation for v = v(z).) (b) (i) Given that -1+4i is a complex root of the cubic polynomial r¹ + 13r-34, determine the other two roots (without using a calculator). (ii) Hence, (and without using a calculator) determine 25 r³+13r-34 dr. 4 (Hint: Use the result of part (a) to write r³+13r-34= (r-a)(r²+bx+c) for some a, b and c, and use partial fractions.)