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secondary 2 | Maths
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Please help me with this factorisation. Thank you very much.
Date Posted: 3 years ago
Views: 461
121 = 11×11 = 11²
x² - 121
= x² - 11²
= (x + 11)(x - 11)
[Recall the property a² - b² = (a + b)(a - b) ]
x² - 121
= x² - 11²
= (x + 11)(x - 11)
[Recall the property a² - b² = (a + b)(a - b) ]
Now notice that 7979 + 121 = 8100
And 8100 = 90 × 90 = 90²
So,
7979
= 8100 - 121
= 90² - 11²
= (90 + 11)(90 - 11)
= (101)(79)
Or 101 × 79
These are your two other factors.
And 8100 = 90 × 90 = 90²
So,
7979
= 8100 - 121
= 90² - 11²
= (90 + 11)(90 - 11)
= (101)(79)
Or 101 × 79
These are your two other factors.
Edited
Alternative way without using part (a)
(For enrichment purposes)
Notice that 7979
= 7900 + 79
= 79 × 100 + 79 × 1
= 79 × (100 + 1)
= 79 × 101
(For enrichment purposes)
Notice that 7979
= 7900 + 79
= 79 × 100 + 79 × 1
= 79 × (100 + 1)
= 79 × 101
See 1 Answer
Answer in main comments.
Thank you for the clear explanations. I appreciated it.
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