It would be useful if you could nail down the source of this tension.

如果你能弄清这种紧张情绪的根源，会是有用的。

《柯林斯英汉双解大词典》

If you don't learn something useful now, you will have difficulty finding a job in the future.

如果你现在不学点有用的东西，将来找工作就会很困难。

youdao

Go out and try different activities, and stick to them if you think they're useful.

走出去，尝试不同的活动，如果你认为它们有用就坚持下去。

youdao

It would be so easy if you built a cohesive system that carries the entire transaction to create a receipt that is useful.

如果你建立一个,能覆盖整个交易过程,能产生有效的收据的系统,一切都会变得更容易。

斯坦福公开课 - Twitter之父Jack.Dorsey演讲：好奇和灵感的力量课程节选

What does come out, which is very useful is, if you do run the reaction, here's how much heat comes out.

能得到的结果是，如果我们进行这个化学反应，有多少热量放出，当然这也是很重要的。

麻省理工公开课 - 热力学与动力学课程节选

Sometimes a blunt cut is useful if you want to sort of grow a sticky end of your choice on it.

这时候钝切口很有用,尤其在你想获得选定的粘性末端的时候

耶鲁公开课 - 生物医学工程探索课程节选

But, a couple of weeks with the gorgeous, if questionably useful device, has started to produce some truly exciting results.

ENGADGET: Nexus Q hacked to launch apps, gets remote control web app HD

Spending a quarter of a century building something and then scuttling it looks bad, even if the useful science that has been done on board could be written up on the back of a postage stamp.

ECONOMIST: Space

These are allies who not only posess the most deployable military forces in Europe, should America need them, but also have influence in parts of the world, from Europe to the Middle East and Asia, that will be equally useful if America's diplomats are to turn the coalition of sympathisers into something more useful and enduring.

ECONOMIST: First, build the coalition. Then, think what to do