Question

√21+√8+√59√+b+√81=5
Options
A) 8
B)4
C) 7
D)3

Answer 1

Given:

The equation  $\sqrt{21}+\sqrt{8}+\sqrt{59}*\sqrt{b}+\sqrt{81} = 5$

To Find:

The value of b.

Solution:

For Finding the value of b,

By using the properties of Square Root,

            $\sqrt{3}*\sqrt{7}+2*\sqrt{2}+\sqrt{59}*\sqrt{b}+\sqrt{9*9}=5\\~~~~1.73*2.64+2*1.41+\sqrt{59}*\sqrt{b}+9=5\\~~~~~~~~~~~~~~~~4.58+2.82+\sqrt{59}*\sqrt{b}+9=5\\~~~~~~~~~~~~~~~~~~~~~~~~~~~~~16.40+\sqrt{59}*\sqrt{b}=5\\~~~~~~~~~~~~~`~~~~~~~~~~~~~~~~~~~~~~~~~~\sqrt{59}*\sqrt{b}=5-16.40\\~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\sqrt{b}=\frac{-11.40}{\sqrt{59}}$

$~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\sqrt{b}=-1.48\\~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~b=(1.48)^2\\b=2.20~~(approx.)$

Hence the calculated value of b is closest to option (D).

So, the correct option is, option (D) 3.

Answer 2

Given :

√21+√8+√59 +√b+√81=5

To Find :

We are required to simplify the above problem and find the value of b.

Solution :

∴ √21+√8+√59√b+√81=5

or,  √59√b = 5 - √81 - √8 - √21

or,  √59√b = 5 - 9 - 2.83 - 4.58

or,  √59√b =  -11.41

or,  √b = $\frac{-11.41}{\sqrt{59} }$

or,     b =  (-1.486)²

∴       b =  2.21

The closest value of b from the given options is (D) that is 3.

Note : The options given is wrong according to me.