√81/196; √1 64/225; (-√15)²; (√4)⁴; (2√7)²; -2√(-7)²; (-2√7)⁴; √676-√576; √9/26*√6,25

1) √(81/196) = √81/√196 = 9/14;

2) √(1 64/225) = √((1 * 225 + 64)/225) = √(289/225) = √289/√225 = 17/15;

3) (-√15)² = 15;

4) (√4)⁴ = 4^(4/2) = 4^2 = 16;

5) (2√7)² = 2 * 2 * 7 = 28;

6) -2√(-7)² = -2 * 7 = -14;

7) (-2√7)⁴ = 2^4 * 7^(4/2) = 16 * 7 * 7 = 784;

8) √676 - √576 = √(26 * 26) - √(24 * 24) =26 - 24 = 2;

9) √9/26 * √6,25 = 3/26 * √(625/100) = 3/26 * 25/10 = (3 * 25)/(26 * 10) = 15/52.