Question

[Mori Ran]

 Bài 1 : Tìm x 

a ) ( x - 1 ) mũ 2 = 49

b ) 3 . ( 13 - x ) mũ 2 = 27

c ) 164 - ( 15 - x ) mũ 3 = 100

d ) ( x + 3 ) mũ 3 - 15 = 210

x mũ 2 : 4 = 16

Answer 1

[Tô Hoài An]

a) \(\left(x-1\right)^2=49\)

\(\Rightarrow\left(x-1\right)^2=7^2=\left(-7\right)^2\)

\(\Rightarrow x-1=7\)                        hoặc                           \(x-1=-7\)

\(x=7+1=8\)                                                                \(x=-7+1=-6\)

Vậy x = 8 hoặc x = - 6

b) \(3\cdot\left(13-x\right)^2=27\)

\(\left(13-x\right)^2=27\div3=9\)

\(\Rightarrow\left(13-x\right)^2=3^2=\left(-3\right)^2\)

\(\Rightarrow13-x=3\)                                          hoặc                                    \(13-x=-3\)

\(x=13-3=10\)                                                                                            \(x=13+3=16\)

Vậy x = 10 hoặc x = 16

c) \(164-\left(15-x\right)^3=100\)

\(\left(15-x\right)^3=164-100=64\)

\(\Rightarrow\left(15-x\right)^3=4^3\)

\(\Rightarrow15-x=4\)

\(x=15-4=11\)

Vậy x = 11

d) \(\left(x+3\right)^3-15=210\)

\(\left(x+3\right)^3=210+15=225\)

\(\Rightarrow\left(x+3\right)^3=...\)

Tương tự mũ lẻ cậu nhé

e) \(x^2\div4=16\)

\(x^2=16\cdot4=64\)

\(\Rightarrow x^2=8^2=\left(-8\right)^2\)
Vậy x = 8 hoặc x = - 8

Answer 2

[Phạm Huyền Trang]

a/\(\left(x-1\right)^2\)=49

\(\left(x-1\right)^2\)=\(7^2\)

=>x-1=7

x=7+1

x=8

b/3.\(\left(13-x\right)^2\)=27

\(\left(13-x\right)^2\)=27:3

\(\left(13-x\right)^2\)=9

\(\left(13-x\right)^2\)=\(3^2\)

=>13-x=3

x=13-3

x=10

c/164-\(\left(15-x\right)^3\)=100

\(\left(15-x\right)^3\)=164-100

\(\left(15-x\right)^3\)=64

\(\left(15-x\right)^3\)=\(4^3\)

=>15-x=4

x=15-4

x=11

d/\(\left(x+3\right)^3\)-15=210

\(\left(x+3\right)^3\)=210+15

\(\left(x+3\right)^3\)=225

sai đề bài câu d hay sao ý bạn ạ 

chỉ có \(\left(x+3\right)^2\)thì mới tính được

e/\(x^2\):4=16

\(x^2\)=16.4

\(x^2\)=64

\(x^2\)=\(8^2\)

=>x=8