Toán Lớp 6: Bài 1: tìm x biết
a) 6x/2.8 + 6x/8.14 + 6x/14.20 + 6x/20.26 = 9/22
b) x+6/x-9 = 11/12
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Toán Lớp 6: Bài 1: tìm x biết
a) 6x/2.8 + 6x/8.14 + 6x/14.20 + 6x/20.26 = 9/22
b) x+6/x-9 = 11/12
Giải giúp mik 2 câu này với hứa cho ctlhn
Comments ( 2 )
⇒ x. ($\frac{6x}{2.8}$ + $\frac{6x}{8.14}$ + $\frac{6x}{14.20}$ + $\frac{6x}{20.26}$) = $\frac{9}{22}$ ⇒ x. [( $\frac{1}{2}$ – $\frac{1}{8}$ )+( $\frac{1}{8}$ – $\frac{1}{14}$ )+( $\frac{1}{14}$ – $\frac{1}{20}$ )+( $\frac{1}{20}$ – $\frac{1}{26}$ )]= $\frac{9}{22}$
⇒ x. ( $\frac{1}{2}$ – $\frac{1}{8}$ + $\frac{1}{8}$ – $\frac{1}{14}$ + $\frac{1}{14}$ – $\frac{1}{20}$ + $\frac{1}{20}$ – $\frac{1}{26}$ )= $\frac{9}{22}$
⇒ x. [( $\frac{-1}{8}$ + $\frac{1}{8}$ )+( $\frac{-1}{12}$ + $\frac{1}{14}$ )+( $\frac{-1}{20}$ + $\frac{1}{20}$ )+( $\frac{-1}{2}$ – $\frac{1}{26}$ )]= $\frac{9}{22}$
⇒ x. ( $\frac{1}{2}$ – $\frac{1}{26}$ ) = $\frac{9}{22}$
⇒ x. ( $\frac{13}{26}$ – $\frac{1}{26}$ ) = $\frac{9}{22}$
⇒ x. $\frac{12}{26}$ = $\frac{9}{22}$
⇒ x = $\frac{9}{22}$ : $\frac{12}{26}$
⇒ x = $\frac{9}{22}$ . $\frac{26}{12}$
⇒ x = $\frac{13}{1}$ . $\frac{13}{4}$
⇒ x = $\frac{39}{44}$
b) $\frac{x+6}{x-9}$ = $\frac{11}{12}$
⇒ 12. (x+6) = 11. (x-9)
⇒ 12x + 72 = 11x – 99
⇒ 12x – 11x = -99 – 72
⇒ (12 – 11) = -99 + (-72)
⇒ x = – 171