10th Class Mathematics Polynomials Question Bank Case Based (MCQs) - Polynomials

The flow of the water in the pool is represented by \[{{x}^{2}}-2x-8,\] then its zeroes are:

A) \[2,-4\]

B) \[4,-2\]

C) \[2,-2\]

D) \[-4,-4\]

Correct Answer: B

Solution :

We have,

\[f(x)={{x}^{2}}-2x-8={{x}^{2}}-4x+2x-8\]

\[=x(x-4)+2(x-4)=(x-4)\,(x+2)\]

For the zeroes of \[f(x),\]

\[x-4=0\] or \[x+2=0\]

\[\therefore \,\,\,\,\,\,\,\,\,x=4,-2\]

[\[8=2\times 4=8\times 1\]

\[\therefore \]We will take 2 and 4 as a factors of 8.

So, middle term is \[-2=-4+2\]]

So, option [b] is correct.