Toán Lớp 8: *Rút gọn biểu thức
A/ x(x+1)(7-x)
B/ (2x+1)²+(x-5)(x+5)-x(5x+7)
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Toán Lớp 8: *Rút gọn biểu thức
A/ x(x+1)(7-x)
B/ (2x+1)²+(x-5)(x+5)-x(5x+7)
Comments ( 2 )
= (x² + x)(7 – x)
= 7x² – x³ + 7x – x
= -x³ + 6x² + 7x
B/ (2x+1)²+(x-5)(x+5)-x(5x+7)
= (2x)² + 2 . 2x . 1 + 1² + x² – 5² – 5x² – 7x
= 4x² + 4x + 1 + x² – 25 – 5x² – 7x
= -3x – 24