Tìm x biết : a,$(x+5)^{3}$ =-64 b,$(2x-3)^{2}$ = 9 29/10/2021 Bởi Cora Tìm x biết : a,$(x+5)^{3}$ =-64 b,$(2x-3)^{2}$ = 9
a, ( x + 5 )$^{3}$ = -64 ⇒ ( x + 5 )$^{3}$ = ($-4)^{3}$ ⇒ x + 5 = -4 ⇒ x = -9 b, ( 2x – 3 )$^{2}$ = 9 ⇒ ( 2x – 3 )$^{2}$ = $3^{2}$ hoặc $-3^{2}$ 2x – 3 = 3 2x – 3 = -3 ⇒ 2x = 6 ⇒ 2x = 0 ⇒ x = 3 ⇒ x = 0 Bình luận
`a)(x+5)^3=(-4)^3` `→x+5=-4` `→x=-4-5` `→x=-9` Vậy `x=-9` `b)(2x-3)^2=9` `→(2x-3)^2=3^2` `→` \(\left[ \begin{array}{l}2x-3=3\\2x-3=-3\end{array} \right.\) `→` \(\left[ \begin{array}{l}2x=6\\2x=0\end{array} \right.\) `→` \(\left[ \begin{array}{l}x=3\\x=0\end{array} \right.\) Vậy `x∈{0;3}` Bình luận
a, ( x + 5 )$^{3}$ = -64
⇒ ( x + 5 )$^{3}$ = ($-4)^{3}$
⇒ x + 5 = -4
⇒ x = -9
b, ( 2x – 3 )$^{2}$ = 9
⇒ ( 2x – 3 )$^{2}$ = $3^{2}$ hoặc $-3^{2}$
2x – 3 = 3 2x – 3 = -3
⇒ 2x = 6 ⇒ 2x = 0
⇒ x = 3 ⇒ x = 0
`a)(x+5)^3=(-4)^3`
`→x+5=-4`
`→x=-4-5`
`→x=-9`
Vậy `x=-9`
`b)(2x-3)^2=9`
`→(2x-3)^2=3^2`
`→` \(\left[ \begin{array}{l}2x-3=3\\2x-3=-3\end{array} \right.\)
`→` \(\left[ \begin{array}{l}2x=6\\2x=0\end{array} \right.\)
`→` \(\left[ \begin{array}{l}x=3\\x=0\end{array} \right.\)
Vậy `x∈{0;3}`