Question

a3 +3a2+9a =1 then find a3 +3/a

Answer 1

Answer: $28$

Step-by-step explanation:

Here, the given equation is,

$a^3+3a^2+9a=1$ ------ (1)

$3a\times (a^3+3a^2+9a)=3$

$3a^4+9a^3+27a^2=3a$

$3a^4+9(a^3+3a^2)=3a$

By the equation (1)

$3a^4+9(1-9a)=3a$

$3a^4+9-81a=3a$

$3a^4+9 = 84a$

By dividing each term by 3a,

$a^3+\frac{3}{a}=28$

Hence, the required answer is 28.

Answer 2

Answer:

28

Step-by-step explanation:

Given:-

a3+3a2+9a=1  

Take ‘ a’ as common:-

a(a2+3a+9)=1  

Dividing both sides by a:

⟹a(a2+3a+9)a=1a  

⟹a2+3a+9=1a  

⟹1a=a2+3a+9  

Multiplying both sides by 3:-

⟹3a=3a2+9a+27⟹(1)  

We know that:-

a3+3a2+9a=1  

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

a3=1–3a2–9a⟹(2)  

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

⟹a3+3a=3a2+9a−3a2−9a+27+1  

⟹a3+3a=27+1⟹28.