# Mathematics: Post your doubts here!

#### Thought blocker

Can anybody pleases help me in part ii

View attachment 65093
Let f(x) = kx³ + 5x² + 10x + 4
According to factor theorem, f(-1 + √3 i) = 0

Thus,
k(-1 + √3 i)³ + 5(-1 + √3 i)² + 10(-1 + √3 i) + 4 = 0

Now solve for k,
k = 2

So, f(x) = 2x³ + 5x² + 10x + 4
Also, f(x) = {x - (-1 + √3 i)}{x - (-1 - √3 i)}{Ax + B}

f(x) = {x² + 2x + 4}{Ax + B} = Ax³ + (B + 2A)x² + (2B + 4A)x + 4B

Compare coefficient of x³: A = 2
Compare constant: B = 1

f(x) = (x² + 2x + 4)(2x + 1)
Thus, third root is -1/2.

#### Thought blocker

• PlanetMaster

#### Varun_bzl

Sorry, my mistake. Thanks

• Thought blocker

#### maniali123321

Re: Maths help available here!!! Stuck somewhere?? Ask here!

Assalamoalaikum!!

Sure..anytime!  sure

#### A*(a*)

Is there any whatsapp group for this group and if yes can someone kindly add me over there
Should I tell my whatsapp number

#### Thought blocker

Is there any whatsapp group for this group and if yes can someone kindly add me over there
Should I tell my whatsapp number
All Whatsapp groups are full but you can join our new Telegram group for A level Mathematics.

#### A*(a*)

Can you please add me in whatsapp group because it suits me more, please remove someone who remains unactive
My whatsapp number is 03312554880
Pleasee   