Toán 8 - hàng đẳng thức : thực hiện phép tính:
a. (x+1)(x^2-x+1)-(x-1)(x^2+x+1)
b. (x^2+2x+1)^2+(2x+1)^2-2(x^2+2x+1)(2 x+1)
c. -3x(x^2)^2+(x+3)(x-1)(x+1)-(2x-3)^2
d. (2x-3)^3+(4-2x)(16+8x+4x^2)+(4x+3)( 9x+1)
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If 10 men take 18 days to mow 60 acres of grass, how long will 15 men take to mow 80 acres?

Which situation can be modeled by the inequality 5 + 10w ≥ 45? a. you start with $5 and save $10 a week until you have at least $45. b.you start with 5 baseball cards and purchase 10 cards every week until you have at most 45 cards. c.you start with 5 water bottles and purchases cases of 10 water bottles each until you have a total of 45 water bottles. d.you spend $5 plus $10 per week until you have less than $45.

Joanie wrote a letter that was 1 1/4 pages long. katie wrote a letter that was 3/4 page shorter then joagies letter. how long was katies letter