Question

25. If (a + b) = 8 and ab =12, find the value of a3 - b3.
[Hint: (a - b)2 = (a + b)2 – 4ab]
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Answer 1

Answer:

Step-by-step explanation:

a + b = 8 |given|

ab = 12

•°• we know that

a³ + b ³ = (a + b ) ( a² + b² - ab )

and , ( a + b ) ²- 2ab = a² + b²

so , a³ + b³= ( a + b ){ ( a + b )² - 3ab }

hence , a³ + b³ = 8{8²- 3 ×12 } ✔ putting the given value

=> 8 { 64- 36}

=> 8×28

= > 224 Answer

a³ + b³ = 224 Answer