Giaỉ phương trình: căn bậc hai

T

tranvanhung7997

$$3{x}^{2} + 4x + 10 = 2 \sqrt{14{x}^{2} - 7}$$
$$<=> 9x^4 + 24 x^3 + 76x^2 + 80x + 100 = 56x^2 - 28$$
$$<=> 9x^4 + 24x^3 + 20x^2 + 80x + 128 = 0$$
$$<=> (x + 2)^2(9x^2 - 12x + 32) = 0$$
$$<=> x + 2 = 0$$
$$<=> x = -2$$
 
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