X/3=y/8=z/5 và 2x+3y-z=50

Step-by-step explanation:

z = 5y/8

x = 3y/8

2x + 3y - z = 50

6y/8 + 3y - 5y/8 = 50

6y/8 + 24y/8 - 5y/8 = 50

25y/8 = 50

25y = 400

y = 16

x = 3y/8 = 3×16/8 = 3×2 = 6

z = 5y/8 = 5×16/8 = 5×2 = 10

- 2 + 10x³ - 21x² + 19x - 4

step-by-step explanation:

each term in the second factor is multiplied by each term in the first factor

x²(- 2x² + 4x - 1) - 3x(- 2x² + 4x - 1) + 4(- 2x² + 4x - 1) ← distribute

= - 2 + 4x³ - x² + 6x³ - 12x² + 3x -8x² + 16x - 4

collect like terms

= - 2 + 10x³ - 21x² + 19x - 4 ← in standard form

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step-by-step explanation: