consider...useful/consider...helpful.
用think也可以.
例句：
I consider it useful performing the experiment.
我认为做这试验是有用的.
When do you think we've going to get onto something useful?
你我认为我们什么时候开始干有用的事呢?
我认为这很有用 I think it helps
consider...useful/consider...helpful.
用think也可以.
例句：
I consider it useful performing the experiment.
我认为做这试验是有用的.
When do you think we've going to get onto something useful?
你我认为我们什么时候开始干有用的事呢?
我认为这很有用 I think it helps