2. Use the choose-an-element method to prove each of the following: (a) ˚ x 2 R j x 2 3x 10 < 0 D fx 2 R j 2 < x < 5g (b) ˚ x 2 R j x 2 5x C 6 < 0 D fx 2 R j 2 < x < 3g (c) ˚ x 2 R j x 2 4 D fx 2 R j x 2g [ fx 2 R