Toán Lớp 8: tìm x 64x³ – 48x² + 12 – 28 = 0
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Toán Lớp 8: tìm x 64x³ – 48x² + 12 – 28 = 0
Em cảm ơn trước ạ
Comments ( 1 )
<=> 16 [ 4x^2 (x-1) +(x-1)(x+1)] = 0
Xét
4x^2 + x + 1
= 4(x^2 + 1/4 . x + 1/4)
Vì: (x+1/8)^2 \ge 0 AA x -> 4(x+1/8)^2 + {15}/{16} \ge {15}/{16} > 0 AA x
-> x – 1 = 0