Toán Lớp 8: khai triển hằng đẳng thức
a, 125x^3 – 1
b, 8x^3 + 125
c, x^3 + y^3/8
d, y^3 – 27x^3
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Toán Lớp 8: khai triển hằng đẳng thức
a, 125x^3 – 1
b, 8x^3 + 125
c, x^3 + y^3/8
d, y^3 – 27x^3
Comments ( 2 )
text{125x³ – 1}
text{= (5x)³ – 1³}
text{=(5x – 1)(25x² + 5x + 1)}
b)
text{8x³ + 125}
text{=(2x)³ + 5³}
text{=(2x + 5)(4x² – 10x + 25)}
d) text{y³ – 27x³}
text{=y³ – (3x)³}
text{=(y – 3x)(y² + 3xy + 9x²)}
c) x³ + y³/8
=x³ + (y/2)³
= (x + y/2)(x² – (xy)/2 + (y²)/4
= (5x)³ – 1³
=(5x – 1)(25x² + 5x + 1)
b)8x³ + 125
=(2x)³ + 5³
=(2x + 5)(4x² – 10x + 25)
d) {y³ – 27x³
=y³ – (3x)³
=(y – 3x)(y² + 3xy + 9x²)
chủ tus ơi , phần c) đề sai sai