Toán Lớp 7: Đề bài: Tìm x, biết:
a, 2x – (-3x – 17) = 53 – 26 – x
b, 5x – (-24) = 33 – 78 + 4x
c, $x^{15}$ = x
d, $(2x+1)^{3}$ = 125
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Toán Lớp 7: Đề bài: Tìm x, biết:
a, 2x – (-3x – 17) = 53 – 26 – x
b, 5x – (-24) = 33 – 78 + 4x
c, $x^{15}$ = x
d, $(2x+1)^{3}$ = 125
Comments ( 2 )
=>2x+3x+17=53-26-x
=>5x+x=27-17
=>6x=10
=>x=5/3
Vậy x=5/3
b) 5x-(-24)=33-78+4x
=>5x+24=33-78+4x
=>5x-4x=-45-24
=>x=-69
Vậy x=-69
c) x^{15}=x
=>x^{15}-x=0
=>x(x^{14}-1)=0
=>\(\left[ \begin{array}{l}x=0\\\\x^{14}-1=0\end{array} \right.\)
=>\(\left[ \begin{array}{l}x=0\\\\x^{14}=1\end{array} \right.\)
=>\(\left[ \begin{array}{l}x=0\\x=-1\\x=1\end{array} \right.\)
Vậy x=0 hoặc x=1 hoặc x=-1
d) (2x+1)^3=125
=>(2x+1)^3=5^3
=>2x+1=5
=>2x=5-1
=>2x=4
=>x=2
Vậy x=2