Toán Tính tích : 2^2/1×3 x 3^2/2×4 x 4^2/3×5 …… 20^2/19×21 24/07/2021 By Aaliyah Tính tích : 2^2/1×3 x 3^2/2×4 x 4^2/3×5 …… 20^2/19×21
Đáp án: `↓ ↓ ↓ ↓ ` Giải thích các bước giải: `2^2/1.3 . 3^2/2.4 . 4^2/3.5 …… 20^2/19.21` `⇔ “\frac{2^2 . 3^2 . 4^2 5^2 … 19^2 . 20^2}{1.2.3^2 . 4^2 .. 19^2 . 20^2 . 21^1 }` `⇔` `\frac{2}{1.21}` = `2/21` Trả lời
Đáp án: $\begin{array}{l}\frac{{{2^2}}}{{1.3}}.\frac{{{3^2}}}{{2.4}}.\frac{{{4^2}}}{{3.5}}…\frac{{{{20}^2}}}{{19.21}}\\ = \frac{{{2^2}{{.3}^2}{{.4}^2}{{…19}^2}{{.20}^2}}}{{{{1.2.3}^2}{{.4}^2}{{…19}^2}{{.20}^2}.21}}\\ = \frac{2}{{1.21}}\\ = \frac{2}{{21}}\end{array}$ Trả lời
Đáp án:
`↓ ↓ ↓ ↓ `
Giải thích các bước giải:
`2^2/1.3 . 3^2/2.4 . 4^2/3.5 …… 20^2/19.21`
`⇔ “\frac{2^2 . 3^2 . 4^2 5^2 … 19^2 . 20^2}{1.2.3^2 . 4^2 .. 19^2 . 20^2 . 21^1 }`
`⇔` `\frac{2}{1.21}` = `2/21`
Đáp án:
$\begin{array}{l}
\frac{{{2^2}}}{{1.3}}.\frac{{{3^2}}}{{2.4}}.\frac{{{4^2}}}{{3.5}}…\frac{{{{20}^2}}}{{19.21}}\\
= \frac{{{2^2}{{.3}^2}{{.4}^2}{{…19}^2}{{.20}^2}}}{{{{1.2.3}^2}{{.4}^2}{{…19}^2}{{.20}^2}.21}}\\
= \frac{2}{{1.21}}\\
= \frac{2}{{21}}
\end{array}$