Toán Lớp 6: Tìm số nguyên x, biết:
a)250:( x- 5) = 64-14
b. 3.( x+8)=17 +(- 23)
c. 2.( x+3)^2= ( -3)^2 -1
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Toán Lớp 6: Tìm số nguyên x, biết:
a)250:( x- 5) = 64-14
b. 3.( x+8)=17 +(- 23)
c. 2.( x+3)^2= ( -3)^2 -1
Comments ( 2 )
a)250:( x- 5) = 64-14
250:( x- 5) = 50
x-5=250:50
x-5=5
x=5+5
x=10
b. 3.( x+8)=17 +(- 23)
3.( x+8)=-6
x+8=-6:3
x+8=-2
x=-2-8
x=-10
c. 2.( x+3)^2= ( -3)^2 -1
2.( x+3)^2= 9-1
2.( x+3)^2=8
( x+3)^2=8:2
( x+3)^2=4
( x+3)^2=2^2
⇔x+3=2
x=2-3
x=-1
a) 250 : ( x – 5 ) = 64 – 14
⇒ 250 : ( x – 5 ) = 50
⇒ x – 5 = 250 : 50
⇒ x – 5 = 5
⇒ x = 5 + 5
⇒ x = 10
Vậy , x = 10 .
b) 3 . ( x + 8 ) = 17 + ( – 23 )
⇒ 3 . ( x + 8 ) = – 6
⇒ x + 8 = – 6 : 3
⇒ x + 8 = – 2
⇒ x = – 2 – 8
⇒ x = – 10
Vậy , x = – 10 .
c) 2 . ( x + 3 )^2 = ( – 3 )^2 – 1
⇒ 2 . ( x + 3 )^2 = 9 – 1
⇒ 2 . ( x + 3)^2 = 8
⇒ ( x + 3 )^2 = 8 : 2
⇒ ( x + 3 )^2 = 4
⇒ \(\left[ \begin{array}{l}( x + 3 )^2 = 2^2\\( x + 3 )^2 = ( – 2 )^2\end{array} \right.\)
⇒ \(\left[ \begin{array}{l}x + 3 = 2\\x + 3 = – 2\end{array} \right.\)
⇒ \(\left[ \begin{array}{l}x = – 1\\x = – 5\end{array} \right.\)
Vậy , x ∈ { – 1 ; – 5 }