Question

Bài 1. Tính Nhanh

a,29.31

b,33,3^2-2.33,3.3,3+3,3^2

c, 20,1.19,9

d,37^2+2.37.13+13^2

Giúp mk với ạ!

 

Answer 1

a) \(29.31=\left(30-1\right)\left(30+1\right)=30^2-1=900-1=899\)

b) \(33,3^2-2.33,3.3,3+3,3^2=\left(33,3-3,3\right)^2=30^2=900\)

c) \(20,1.19,9=\left(20+0,1\right)\left(20-0,1\right)=20^2-0,1^2=400-0.01=399,99\)

d) \(37^2+2.37.13+13^2=\left(37+13\right)^2=50^2=2500\)

Answer 2

a, \(29.31=\left(30-1\right)\left(30+1\right)=30^2-1=899\)

b, \(33,3^2-2.33,3.3,3+3,3^2=\left(33,3-3,3\right)^2=30^2=900\)

c, \(20,1.19,9=\left(20-0,1\right)\left(20+0,1\right)=20^2-0,1^2=399,99\)

d, \(37^2+2.37.13+13^2=\left(37+13\right)^2=50^2=2500\)

Answer 3

a: \(29\cdot31=30^2-1=900-1=899\)

b: \(33.3^2-2\cdot33.3\cdot3.3+3.3^2\)

\(=\left(33.3-3.3\right)^2\)

=900

c: \(20.1\cdot19.9=20^2-0.1^2=399.9\)

d: \(37^2+2\cdot37\cdot13+13^2=\left(37+13\right)^2=2500\)