Question

Bài 1:Tìm x

a) (x-4)^2 - 36 = 0

b) ( x-8)^2 = 121

c)x^2 + 8x + 16 = 0

d) 4x^2 - 12x = -9

Bài 2: Tính nhanh

a) 75^2 - 25^2

b) 53^2 - 47^2

Answer 1

Bài1:

\(â,\left(x-4\right)^2-36=0\\ \Leftrightarrow\left(x-4\right)^2=36\\ \Leftrightarrow x-4\in\left\{-6;6\right\}\\ \Leftrightarrow x\in\left\{-2;10\right\}\)

Vậy...

b<Tương tự

c,\(x^2+8x+16=0\\ \Leftrightarrow\left(x+4\right)^2=0\\ \Leftrightarrow x+4=0\\ \Leftrightarrow x=-4\)

Vậy...

d,Tương tự

Bài2:

\(a,75^2-25^2\\ =\left(75-25\right)\left(75+25\right)\\ =100.50=5000\)

\(b,53^2-47^2\\ =\left(53-47\right)\left(53+47\right)\\ =6.100=600\)

Answer 2

Bài 1:

a) (x-4)^2 - 36 = 0

=> (x-4)^2 = 36

=> (x-4)^2 = 6^2

=> x-4 = 6

=>x = 2

b) (x-8)^2 = 121

=> (x-8)^2 = 11^2

=> x-8 = 11

=> x = 19

c) x^2 + 8x +16 = 0

=> x( x +8) = -16

=> x = -4

d) 4x^2 - 12x = -9( Mk chưa nghĩ ra !)

Answer 3

Bài 2 :

a) 75^2 - 25^2

= (75-25)(75+25)

=50.100

=5000

b) 53^2 - 47^2

= (53-47)(53+47)

=6.100

=600