7.
1) = 3*(3-√5)/(9-5) = - 3/4*(3-√5)
2) =5*(2+√6)/(4-6) = - 5/2*(2+√6)
3) = 1/6*√(27*6) = 1/6*√(3⁴*2)= 9/6*√2 = 3/2*√2
4) √2/√3 = 1/3*√6
5) = (4-√12)/(16+12) = (4 - √12)/28
6) 4*(6+√7)/29
7) (√5+2) *√3 /6 = 1/6*(√15 + 2√3)
8) √6у/(2*у)
9) 2/√х = (2*√х)/х
8.
ДАНО -5 < k< -4
a) 4 < -k < 5
b) -1/5 < 1/k < -1/4
c) 0 < k+5 < 1
d) 9 < -k+5 < 10
9.
S1 = √10*√14 = √140 = 2*√35 = 2*√3*√7
S2 = 16*√15 =16*√3*√5
S3 = 3*√(2*2*7) = 6*√7