Question

1.Tính/Tính nhanh:

a) Tính: \(\left(x-\dfrac{1}{2}\right)^2\)

b) Tính: \(\left(2x-3y\right)^2\)

c) Tính nhanh: \(99^2\)

2. Tính/ Tính nhanh:

a) Tính \(\left(x+1\right)\left(x-1\right)\)

b) Tính \(\left(x-2y\right)\left(x+2y\right)\)

c) Tính nhanh: 56.54

Giúp em vs ạ, em cảm ơn rất nhìuuuuu

Answer 1

Giải:

Bài 1:

a) \(\left(x-\dfrac{1}{2}\right)^2=x^2-x+\dfrac{1}{4}\)

b) \(\left(2x-3y\right)^2=4x^2-12xy+9y^2\)

c) \(99^2=\left(100-1\right)^2=100^2-200+1^2=10000-200+1=9801\)

Bài 2:

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

b) \(\left(x-2y\right)\left(x+2y\right)=x^2-\left(2y\right)^2=x^2-4y^2\)

c) \(56.64=\left(60-4\right)\left(60+4\right)=60^2-4^2=3600-16=3584\)

Chúc bạn học tốt!

Answer 2

\(\left(x-\dfrac{1}{2}\right)^2=x^2-x+\dfrac{1}{4}\)

\(\left(2x-3y\right)^2=4x^2-12xy+9y^2\)

\(99^2=\left(100-1\right)^2=100^2-200+1=10000-199=9801\)

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

\(\left(x-2y\right)\left(x+2y\right)=x^2-4y^2\)

\(56.54=\left(55+1\right)\left(55-1\right)=55^2-1=3024\)

Answer 3

1.

a)\(\left(x-\dfrac{1}{2}\right)^2\)

=\(x^2-2.x.\dfrac{1}{2}+\left(\dfrac{1}{2}\right)^2\)

=\(x^2-x+\dfrac{1}{4}\)

b)\(\left(2x-3y\right)^2\)

=\(\left(2x\right)^2-2.2x.3y+\left(3y\right)^2\)

=\(4x^2-12xy+9y^2\)

c)99²=(100-1)²=100²-2.100.1+1²=10000-200+1=8000

2.

a)(x-1).(x+1)=x²-1²

b)(x-2y).(x+2y)=x²-2y²

c)Hình như sai đề.