Find the square root of 31-4√21

31+4

21

=28+3+2

4×21

=(

28

)

2

+(

3

)

2

+2

28

×

3

=(

28

+

3

)

2

Using (a+b)

2

=a

2

+b

2

+2ab

31+4

21

=(

28

+

3

)

2

∴

31+4

21

=(

28

+

3

)

The square root of

31+4

21

is (

28

+

3

)

c.

step-by-step explanation:

because first you have to add the 4x, 9x, and the 7x together and you get 20x and then you add the last numbers up and you get 5and then you put the subtraction sign in there and that's how you get the answer.