a) 503= 120 = 623                              b) 732 + 1013 + 2008 = 3753

c) 1000 + 12.80 =1960                       d) 2018 + 120.7 = 2858

e) 96.50 + 25.400 = 14800                  f) 125.80 + 50.20 =11000

a) 503= 120 = 623

b) 732 + 1013 + 2008 = 3753

c) 1000 + 12.80 =1960

d) 2018 + 120.7 = 2858

e) 96.50 + 25.400 = 14800

f) 125.80 + 50.20 =11000

a) 2601.

b) 4033.

c) 12000.

d) 20500.

e)20000.

f) 8000.

a) Trong các phép tính trên, phép tính B, D sai.

b) Sửa

Phép tính B,D sai

a)
\(-7x^2\left(3x-4y\right)\)
\(=-21x^3+28x^2y\)
b)
\(\left(x-3\right)\left(5x-4\right)\)
\(=x\left(5x-4\right)-3\left(5x-4\right)\)
\(=5x^2-4x-15x+12\)
\(=5x^2-\left(4x+15x\right)+12\)
\(=5x^2-19x+12\)

a: =-7x^2*3x+7x^2*4y

=-21x^3+28x^2y

b: =5x^2-4x-15x+12

=5x^2-19x+12

`a, -7x^2(3x-4y)=-21x^3 + 28x^2y`

`b, (x-3)(5x-4) = 5x^2 - 15x - 4x + 12 = 5x^2 - 19x + 12`

a)\(\frac{{ - 2}}{5} + \frac{3}{7} = \frac{{ - 14}}{{35}} + \frac{{15}}{{35}} = \frac{1}{{35}}\)           

b)\(0,123 - 0,234 =  - \left( {0,234 - 0,123} \right) =  - 0,111.\)

a) 20,24 .0,125 = 2,53                     

b) 6,24 : 0,125 = 49,92

c) 2,40. 0,875 = 2,1                         

d) 12,75 : 2,125 = 6.

a)

b) (x – 1)(x + 1)(x² + 1)

= [x .(x + 1) – 1 .(x + 1)] . (x² + 1)

= {x.x + x.1 + (-1).x + (-1).1}. (x² + 1)

= (x² + x – x – 1) . (x² + 1)

= (x² – 1) . (x² + 1)

= x² . (x² +1) – 1.(x² + 1)

= x² . x² + x² . 1 – (1.x² + 1.1)

= x⁴ + x² – (x² + 1)

= x⁴ + x² – x² – 1

= x⁴ – 1

a) (- 45,5) . 0,4 =  - 18,2                         

b) ( - 32,2) . (-0,5) = 16,1

c) (- 9,66) : 3,22 =  -3                            

d) (- 88,24) : (- 0,2) = 441,2.