Toán Lớp 7: a) 2x-1 = 16 b) (x -1)2 = 25 c) (x-1) mũ x+2 = (x-1) mũ x+6 d) (x+20) mũ 100 + | y +4 | = 0

Question

Toán Lớp 7:  a) 2x-1 = 16       b) (x -1)2 = 25   c) (x-1) mũ x+2 = (x-1) mũ x+6  d) (x+20) mũ 100 + | y +4 | = 0

ankim · Answer

a)2x-1=16
=>2x=16+1
=>2x=17
=>x=17/2
Vậy x=17/2
b)(x-1)²=25
=> $\left[ \begin{array}{l}(x-1)²=5²\\(x-1)²=(-5)²\end{array} \right.$
=> $\left[ \begin{array}{l}x-1=5\\x-1=-5\end{array} \right.$
=> $\left[ \begin{array}{l}x=6\\x=-4\end{array} \right.$
Vậy x=6 hoặc x=-4
c)(x-1)^(x+2)=(x-1)^(x+6)
=>(x-1)^(x+2)-(x-1)^(x+6)=0
=>(x-1)^(x+2)-(x-1)^(x+2).(x-1)^4=0
=>(x-1)^(x+2) [1-(x-1)⁴]=0
=> $\left[ \begin{array}{l}(x-1)^{x+2} =0\\1-(x-1)⁴=0\end{array} \right.$
=> $\left[ \begin{array}{l}x-1=0\\(x-1)⁴=1\end{array} \right.$
=> $\left[ \begin{array}{l}x=1\\(x-1)⁴=(±1)⁴\end{array} \right.$
=> $\left[ \begin{array}{l}x=1\\x-1=+-1\end{array} \right.$
=> $\left[ \begin{array}{l}x=1\\x=0\\x=2\end{array} \right.$
Vậy x=1;x=0 hoặc x=2
d)(x+20)^100 +|y+4|=0
Vì (x+20)^100 >=0AAx
|y+4|>=0 AAx
=> $\begin{cases}(x+20)¹⁰⁰ =0\\|y+4|=0\end{cases}$
=> $\begin{cases}x+20=0\\y+4=0\end{cases}$
=> $\begin{cases}x=-20\\y=-4\end{cases}$
Vậy x=-20 và y=-4

myngocla · Answer

Gửi bạn tham khảo !