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

Toán Lớp 7: y = f (x) =2x^2 – 5x a , tìm f(-3) ; f(-1/2) ; f(4/3) b, tìm x biết y = 0

Toán Lớp 7: y = f (x) =2x^2 – 5x
a , tìm f(-3) ; f(-1/2) ; f(4/3)
b, tìm x biết y = 0

Comments ( 2 )

  1. a) F(-3) = 2 . (-3)^2 – 5 . (-3)
    ⇒ F (-3) = 18 – (-15)
    ⇒ F (-3) = 33
    F(-\frac{1}{2}) = 2 . (-\frac{1}{2})^2 – 5 . (-\frac{1}{2})
    ⇒ F(-\frac{1}{2}) = \frac{1}{2} – (-\frac{5}{2})
    ⇒ F(-\frac{1}{2} = 3
    F(\frac{4}{3}) = 2 . (\frac{4}{3})^2 – 5 . \frac{4}{3}
    ⇒ F(\frac{4}{3}) = \frac{32}{9} – \frac{20}{3}
    ⇒ F(\frac{4}{3}) = -28/9
    b) y = 0
    hay 2x^2 – 5x = 0 
    ⇒ x(2x – 5) = 0
    ⇒ x = 0 hoặc 2x – 5 = 0
    ⇒ x = 0 hoặc x = 5/2

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