1) 8x^2y - 4xy^2 - 8x^2y + 2x=> -4xy^2 + 2x
2) x^2 - xyz + y^2 - zxy + z^2 - zxy + 3xyz = x^2 + y^2 + z^2=> -2zxy + 3xyz = 0
3) -20x - 15 + 3x = -12x + 60=> -17x - 15 = -12x + 60=> -5x - 15 = 60=> -5x = 75=> x = -15
1) 8x^2y - 4xy^2 - 8x^2y + 2x
=> -4xy^2 + 2x
2) x^2 - xyz + y^2 - zxy + z^2 - zxy + 3xyz = x^2 + y^2 + z^2
=> -2zxy + 3xyz = 0
3) -20x - 15 + 3x = -12x + 60
=> -17x - 15 = -12x + 60
=> -5x - 15 = 60
=> -5x = 75
=> x = -15