Toán Lớp 6: Tìm x:
a)x+x+x+91=-2
b)(5x+1)^2=121
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Toán Lớp 6: Tìm x:
a)x+x+x+91=-2
b)(5x+1)^2=121
Comments ( 2 )
a)x+x+x+91=-2
3x=-2-91
3x=-93
x=-31
Vậy x=-31
b)(5x+1)^2=121
(5x+1)^2=11^2
⇔5x+1=11
5x=10
x=2
Vậy x=2
a) x+x+x+91=-2
3x+91=-2
3x = -2 – 91
3x = -93
x = -93 : 3
x = -31
Vậy x = -31
b) (5x+1)²=121
(5x+1)²=(±11)²
TH1: 5x + 1 = 11
5x = 11 – 1
5x = 10
x = 10 : 5
x = 2
TH1: 5x + 1 = -11
5x = -11 – 1
5x = -12
x = -12 : 5
x = -12/5
Vậy x ∈ {2; -12/5}
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