The integrating factor to reduce the differential equation xy da + (2x2 + 3y2 - 20) dy = 0 to exact differential equation a) b) v2 c) y d) None of these The integrating factor to reduce the differential equation (x + 3y?)dx + 2xy dy = 0 to exact differential equation b) x2 d) None of these The integrating factor to reduce the differential equation (sin y + x + 2x)dx = cosy dy to exact differential equation a x b) ex c ex d) None of these The integrating factor to reduce the differential equation (y + 2x)dx + x(y + x + 1)dy =0 to exact differential equation a) y b) ey c) ey d) None of these