Question

If 81 a² - b = (9a-1/3) (9a +1/3 ) find b​

Answer 1

Answer:

Given:-

a3+3a2+9a=1a3+3a2+9a=1

Take ‘ a’ as common:-

a(a2+3a+9)=1a(a2+3a+9)=1

Dividing both sides by a:

⟹a(a2+3a+9)a=1a⟹a(a2+3a+9)a=1a

⟹a2+3a+9=1a⟹a2+3a+9=1a

⟹1a=a2+3a+9⟹1a=a2+3a+9

Multiplying both sides by 3:-

⟹3a=3a2+9a+27⟹(1)⟹3a=3a2+9a+27⟹(1)

We know that:-

a3+3a2+9a=1a3+3a2+9a=1

Subtracting both sides by : 3a2+9a3a2+9a we get:-

a3=1–3a2–9a⟹(2)a3=1–3a2–9a⟹(2)

Adding (1) and (2) we get:-

⟹a3+3a=3a2+9a−3a2−9a+27+1⟹a3+3a=3a2+9a−3a2−9a+27+1

⟹a3+3a=27+1⟹28.⟹a3+3a=27+1⟹28.

That’s the answer:-28

Hope it helps:-)