Which of the following is NOT a surd?

A

√9 + √7

B

√9 - √7

C

√(9 + 7)

D

√(9 - 7)

head- to- toes-smart
Jul 26, 2014

#1**+10 **

C is not a surd.

sqrt(9+7) = sqrt(16) = 4

The rest are decimals since they cannot be simplified to remove the sqrt symbol.

sqrt(9) by itself is not a surd, but with the + / - sqrt(7) [which cannot be simplified like sqrt(4), sqrt(25), etc.] it is a surd.

AzizHusain
Jul 26, 2014

#2**+10 **

I've not run across the term "surd" before......Simply put, it is a number that cannot be simpified to remove a root (an irrational number is the result).....

How did we get the word "Surd" ?

Well around 820 AD *al-Khwarizmi* (the Persian guy who we get the name "Algorithm" from) called irrational numbers "'inaudible" ... this was later translated to the Latin * surdus* ("deaf" or "mute")

BTW......Thanks Aziz, for that answer........

CPhill
Jul 27, 2014