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中4a-maths,唔該大家啊,help me

發問:

試寫出下列各式的展開式中所求的項之(係數)或(常數項) (x^2+2)^6 ,x^6項 (2x+y)^10 ,x^3y^7項 (1/2-3x)^8 ,x^3項

最佳解答:

1. (x2 + 2)6 General term, (r + 1)th term = 6Cr (x2)6-r(2)r = (2)r 6Cr (x12-2r) For x6 term, 12 – 2r = 6 r = 3 So, the coefficient of x6 term = 23 6C3 = 160 2. (2x + y)10 General term, (r + 1)th term = 10Cr (2x)10-r (y)r = (2)10-r 10Cr x10-ryr For x3y7 term, 10 – r = 3 r = 7 So, the coefficient of x3y7 term = 210-7 10C7 = 960 3. (1/2 – 3x)8 General term, (r + 1)th term = 8Cr (1/2)8-r (-3x)r = (1/2)8-r (-3)r 8Crxr For x3 term, r = 3 So, the coefficient of x3 term = (1/2)8-3 (-3)3 8C3 = -189/4

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中4a-maths,唔該大家啊,help me 用nCr , (n+1) tern 那方法計63D0B758E2D502CC
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