$\frac{1}{a^{2} }$ – $\frac{1}{( \frac{√5}{2})^{2} }$ = ? 02/09/2021 Bởi Ximena $\frac{1}{a^{2} }$ – $\frac{1}{( \frac{√5}{2})^{2} }$ = ?
`1/a^2-1/((sqrt5/2)^2)` `=(1/a)^2-(1/(sqrt5/2))^2` `=(1/a)^2-(1*2/sqrt5)^2` `=(1/a)^2-(2/sqrt5)^2` `=(1/a-2/sqrt5)(1/a+2/sqrt5)` Bình luận
ĐK: $a\neq 0$ $\dfrac{1}{a^2}-\dfrac{1}{(\frac{\sqrt5}{2})^2}$ $=(\dfrac{1}{a})^2 – (\dfrac{1}{\frac{\sqrt5}{2}})^2$ $=(\dfrac{1}{a})^2 – (\dfrac{2}{\sqrt5})^2$ $=(\dfrac{1}{a}-\dfrac{2}{\sqrt5})(\dfrac{1}{a}+\dfrac{2}{\sqrt5})$ Bình luận
`1/a^2-1/((sqrt5/2)^2)`
`=(1/a)^2-(1/(sqrt5/2))^2`
`=(1/a)^2-(1*2/sqrt5)^2`
`=(1/a)^2-(2/sqrt5)^2`
`=(1/a-2/sqrt5)(1/a+2/sqrt5)`
ĐK: $a\neq 0$
$\dfrac{1}{a^2}-\dfrac{1}{(\frac{\sqrt5}{2})^2}$
$=(\dfrac{1}{a})^2 – (\dfrac{1}{\frac{\sqrt5}{2}})^2$
$=(\dfrac{1}{a})^2 – (\dfrac{2}{\sqrt5})^2$
$=(\dfrac{1}{a}-\dfrac{2}{\sqrt5})(\dfrac{1}{a}+\dfrac{2}{\sqrt5})$