Cho a,b,c > 0 t/m c^2 = a^3 + b^3 = 3ab + c Cho a,b,c > 0 t/m c^2 = a^3 + b^3 = 3ab + c. CMR : 2.a^2b^2 + 2.b^2c^2 + 2.c^2a^2 = a^4+b^4+c^4 help!!!
Tham khảo câu trả lời từ Trợ lý ảo Lazi To analyze the conditions given in the problem, let's first rewrite the relations based on the assumptions: 1. \( c^2 = a^3 + b^3 \) 2. \( c^2 = 3ab + c \) From the first equation, we can express \( c \) as: \[ c = \sqrt{a^3 + b^3} \] Substituting \( c \) into the second equation gives: \[ a^3 + b^3 = 3ab + \sqrt{a^3 + b^3} \] To solve this, we set \( x = c^2 \), leading to: \[ x = a^3 + b^3 \] And from the second equation: \[ x = 3ab + \sqrt{x} \] This gives us a non-linear equation in terms of \( x \): \[ x - \sqrt{x} - 3ab = 0 \] Let \( t = \sqrt{x} \), giving: \[ t^2 - t - 3ab = 0 \] We can solve this for \( t \) using the quadratic formula: \[ t = \frac{1 \pm \sqrt{1 + 12ab}}{2} \] Since \( t \) (which is \( \sqrt{x} \)) must be positive, we take the positive root: \[ t = \frac{1 + \sqrt{1 + 12ab}}{2} \] Now squaring \( t \), we find \( c^2 = x = t^2 \): \[ c^2 = \left(\frac{1 + \sqrt{1 + 12ab}}{2}\right)^2 = \frac{(1 + \sqrt{1 + 12ab})^2}{4} \] Calculating this results in: \[ c^2 = \frac{1 + 2\sqrt{1 + 12ab} + (1 + 12ab)}{4} = \frac{2 + 12ab + 2\sqrt{1 + 12ab}}{4} \] At this step, we've derived an expression for \( c^2 \) in terms of \( a \) and \( b \). Given the challenge to prove or derive other conditions like \( 2a^2b^2 + 2b^2c^2 + 2c^2a^2 = a^4 + b^4 + c^4 \), we can apply algebraic manipulations or symmetry properties among \( a, b, c \). From the initial conditions used, we can derive more expressions or utilize relationships such as the AM-GM inequality. You may employ numerical values or specific scenarios for \( a, b, c \) to explore scenarios in proving symmetric properties. The main approach revolves around inter-relating these variables and checking for identities or symmetries between them, which can lead to proving the equality you've presented. Due to the complexity of \( CMR : 2.a^2b^2 + 2.b^2c^2 + 2.c^2a^2 = a^4 + b^4 + c^4 \), you may wish to expand both sides and try comparing coefficients or using specific values for \( a, b, \) and \( c \) to verify. An algebraic proof may utilize variable substitutions or inequalities, depending on how you proceed with simplifications from known relations.