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secondary 2 | Maths
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Mirandi
Mirandi

secondary 2 chevron_right Maths chevron_right Singapore

Please help to answer question b). Thanks in advance!

Date Posted: 3 months ago
Views: 38
J
J
3 months ago
a² - b² = (a + b)(a - b)

308² + 307² - 306² - 305²

= 308² - 306² + 307² - 305²

= (308 - 306)(308 + 306) + (307 - 305)(307 + 305)

= 2 x 614 + 2 x 612
= 2 x (614 + 612)

= 2 x 1226
= 2452
J
J
3 months ago
Or

(a + b)² = a² + 2ab + b²

308² + 307² - 306² - 305²

= (306 + 2)² - 306² + (305 + 2)² - 305²

= 306² + 2(2)(306) + 2² - 306² + 305² + 2(2)(305) + 2² - 305²

= 1224 + 4 + 1220 + 4
= 2452
Eric Nicholas K
Eric Nicholas K
3 months ago
Or (308^2 - 305^2) + (307^2 - 306^2).

Mirandi, you can attempt this third option on your own.
J
J
3 months ago
And one more option :

(a - b)² = a² - 2ab + b²

308² + 307² - 306² - 305²

= 308² - (308 - 2)² + 307² - (307 - 2)²

= ...

=...

= 2452

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Claudine Lim
Claudine Lim's answer
16 answers (Tutor Details)
1st
tip: need to look for similarities between part a and b
Mirandi
Mirandi
3 months ago
Thanks!