Toán Lớp 7: Tìm x; y biết:
a. . 25 – y2 = 8( x – 2009)
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Toán Lớp 7: Tìm x; y biết:
a. . 25 – y2 = 8( x – 2009)
Comments ( 1 )
$ 25 – y^2 = 8 . ( x – 2009 ) $
$ y^2 ≥ 0 ⇒ x – 2009 ≤ \sqrt[]{\dfrac{25}{8}} $
$ ⇒ $ \(\left[ \begin{array}{l}x-2009=0\\x-2009=1\end{array} \right.\)
$ x – 2009 = 0 ⇒ 25 – y^2 = 0 ⇒ y^2= 25 ⇒ y = ±5 $
$ x – 2009 = 1 ⇒ 25 – y^2 =8 ⇒ y^2 = 17 ⇒ y=\sqrt[]{17} $
$ ⇒ [ ( x – 2009 ) ; y ] = ( 0 ; 5 ) ; ( 0 ; -5 ) ⇒ ( x; y ) = ( 2009 ; 5 ) ; ( 2009 ; -5 ) $