Let's start by imagining a rock being thrown to the air. Let's say that going up is the positive direction and so, going down is the negative. The acceleration is pointing down (because of gravity) so it's always negative. While the rock is going up, it's velocity/speed is positive, but the acceleration is negative. While the rock is going down, both acceleration and speed are negative. This shows that the first statemente is true, but the second is false. You can also think that if you define going DOWN as the POSITIVE direction, you can have both positive acceleration and speed, or positive acceleration and negative speed.
Technology can be both negative and positive when it comes to modified crops. It can be positive because it allows us to have more crops and resist pests and disease. It can be negative because it may cause deformities or health risks.
