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प्रश्न
Subtract b(b2 + b – 7) + 5 from 3b2 – 8 and find the value of expression obtained for b = – 3.
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उत्तर
We have,
Required difference = (3b2 – 8) – [b(b2 + b – 7) + 5]
= 3b2 – 8 – b(b2 + b – 7) – 5
= 3b2 – 8 – b3 – b2 + 7b – 5
= – b3 + 2b2 + 7b – 13
Now, If b = – 3
The value of above expression = – (–3)3 + 2(–3)2 + 7(–3) – 13
= – (–27) + 2 × 9 – 21 – 13
= 27 + 18 – 21 – 13
= 45 – 34
= 11
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