Cho hai số hữu tỷ a, b thỏa mãn |a + b| = |a − b|. Chứng minh a = 0 hoặc b = 0.
II. Place (‘) on the main stress of each word below.
Eg: ‘interesting
recognize | understand | heavy | factory | humans | able | robot |
complicated | conversation | essay | useful | laundry | scientist | coffee |
improve | problem | message | because | mobile | around | even |