tìm x biết : ( 1/199*197 – 1/197*195 – …… – 1/5*3 – 1/3*1 )*(x-1) = 2 26/08/2021 Bởi Lydia tìm x biết : ( 1/199*197 – 1/197*195 – …… – 1/5*3 – 1/3*1 )*(x-1) = 2
$(\frac{1}{199*197}-\frac{1}{197*195}-…-\frac{1}{5*3}-\frac{1}{3*1})(x-1)=2$ $⇔(\frac{2}{199*197}-\frac{2}{197*195}-…-\frac{2}{5*3}-\frac{2}{3*1})(x-1)=4$ $⇔(\frac{1}{199}-\frac{1}{197}-\frac{1}{197}+\frac{1}{195}-…-\frac{1}{5}+\frac{1}{3}-\frac{1}{3}+1)(x-1)=4$ $⇔(\frac{1}{199}-\frac{2}{197}+1)(x-1)=4$ $⇔1(x-1)≈4$ $⇔x-1≈4$ $⇔x≈4+1=5$ Bình luận
Đáp án: `( 1/199`x`197 – 1/197`x`195 – …… – 1/5`x`3 – 1/3`x`1 ).(x-1) = 2` `- ( 1/199`x`197 + 1/197`x`195 + …… + 1/5`x`3 + 1/3`x`1 ).(x-1)=2` `- ( 1/199 – 1/197 + 1/197 – 1/195 +… + 1/5 – 1/3 + 1/3 – 1 ).(x-1)=2` `- ( 1/199 – 1).(x-1)=2` `198/199.(x-1)=2` `x-1 = 199/99` `x= 298/99` Học tốt ! Bình luận
$(\frac{1}{199*197}-\frac{1}{197*195}-…-\frac{1}{5*3}-\frac{1}{3*1})(x-1)=2$
$⇔(\frac{2}{199*197}-\frac{2}{197*195}-…-\frac{2}{5*3}-\frac{2}{3*1})(x-1)=4$
$⇔(\frac{1}{199}-\frac{1}{197}-\frac{1}{197}+\frac{1}{195}-…-\frac{1}{5}+\frac{1}{3}-\frac{1}{3}+1)(x-1)=4$
$⇔(\frac{1}{199}-\frac{2}{197}+1)(x-1)=4$
$⇔1(x-1)≈4$
$⇔x-1≈4$
$⇔x≈4+1=5$
Đáp án:
`( 1/199`x`197 – 1/197`x`195 – …… – 1/5`x`3 – 1/3`x`1 ).(x-1) = 2`
`- ( 1/199`x`197 + 1/197`x`195 + …… + 1/5`x`3 + 1/3`x`1 ).(x-1)=2`
`- ( 1/199 – 1/197 + 1/197 – 1/195 +… + 1/5 – 1/3 + 1/3 – 1 ).(x-1)=2`
`- ( 1/199 – 1).(x-1)=2`
`198/199.(x-1)=2`
`x-1 = 199/99`
`x= 298/99`
Học tốt !