If a, B ∈ R, and 4 ≤ A2 + B2 ≤ 9, then the sum of the maximum and minimum of A2 AB + B2 is______ ．

If a, B ∈ R, and 4 ≤ A2 + B2 ≤ 9, then the sum of the maximum and minimum of A2 AB + B2 is______ ．

∵ (a + b) 2 ≥ 0 or (a-b) 2 ≥ 0, ∵ (A2 + B2) ≤ 2Ab ≤ A2 + B2, ∵ 4 ≤ A2 + B2 ≤ 9, then - 9 ≤ 2Ab ≤ 4 can be obtained, the solution can be obtained, - 92 ≤ ab ≤ 2, ∵ - 2 ≤ - AB ≤ 92, ∵ - 2 + 4 ≤ A2 AB + B2 ≤ 92 + 9, that is, 2 ≤ A2 AB + B2 ≤ 272

Elden Ring Premiere

RELATED INFORMATIONS