Question

Write the answer in simplified radical form

Answer 1

2√3

Explanation:

subtract the numbers 21 - 9 = 12

do prime factorization 2² * 3

then apply the radical rule

√2² = 2

2√3

I hope this helps! :)

Answer 2

Put x = 9 to the expression:

`√(21-x)\to√(21-9)=√(12)=√(4\cdot3)=\sqrt4\cdot\sqrt3=2\sqrt3`

`Used\ √(ab)=√(a)\cdot√(b)\\\\\sqrt4=2\ \text{because}\ 2^2=4`