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222-9+11+12:2*14+14 = ? ( )

Toán Lớp 7: Chứng minh rằng nếu `a/b = c/d` thì: `(5a + 3b)/(5a – 3b) = (5c + 3d)/(5c – 3d)`

Toán Lớp 7: Chứng minh rằng nếu a/b = c/d thì: (5a + 3b)/(5a – 3b) = (5c + 3d)/(5c – 3d)

Comments ( 2 )

  1. Sửa đề : (5a+33b)/(5a-3b) to (5a+3b)/(5a-3b)
    Đặt a/b=c/d=k
    to {(a=bk),(c=dk):}
    =>
    (5a+3b)/(5a-3b) \ = (5bk+3b)/(5bk-3b)
    \qquad\qquad\qquad\qquad=(b(5k+3))/(b(5k-3))=(5k+3)/(5k-3) \ \ (2)
    (5c+3d)/(5c-3d) \ = (5dk+3d)/(5dk-3d)
    \qquad\qquad\qquad\qquad=(d(5k+3))/(d(5k-3))=(5k+3)/(5k-3) \ \ (2)
     Từ (1) và (2) to (5a+3b)/(5a-3b)=(5c+3d)/(5c-3d)

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222-9+11+12:2*14+14 = ? ( )

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