Toán Lớp 9: Rút gọn
a) √9a – √16a + √49a. (Với a>=0)
b) 2√40√12 – 2√√75 – 3√5√48
c) (4√x – √2x) (√x – √2x) (với x>0)
d) (2√x + √y ) ( 3√x – 2√y ) (x>=0 ; y>=0)
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Toán Lớp 9: Rút gọn
a) √9a – √16a + √49a. (Với a>=0)
b) 2√40√12 – 2√√75 – 3√5√48
c) (4√x – √2x) (√x – √2x) (với x>0)
d) (2√x + √y ) ( 3√x – 2√y ) (x>=0 ; y>=0)
Comments ( 2 )
a)6\sqrt a \\
c)2x – 5x\sqrt 2 \\
d)6x – \sqrt {xy} – 2y
\end{array}\)
a)\sqrt {9a} – \sqrt {16a} + \sqrt {49a} \\
= 3\sqrt a – 4\sqrt a + 7\sqrt a \\
= 6\sqrt a \\
c)\left( {4\sqrt x – \sqrt {2x} } \right)\left( {\sqrt x – \sqrt {2x} } \right)\\
= 4x – 4x\sqrt 2 – x\sqrt 2 – 2x\\
= 2x – 5x\sqrt 2 \\
d)\left( {2\sqrt x + \sqrt y } \right)\left( {3\sqrt x – 2\sqrt y } \right)\\
= 6x – 4\sqrt {xy} + 3\sqrt {xy} – 2y\\
= 6x – \sqrt {xy} – 2y
\end{array}\)