a)2x²-2xy

b)9-x²

c)10012

(Câu c là sao?)

a) \(2x\left(x-y\right)=2x^2-2xy\)

b) \(\left(3+x\right)\left(3-x\right)=3^2-x^2=9-x^2\)

Các bạn giúp mik đi ạ, mik đang cần gấp nhất là câu c ạ

\(=\dfrac{3}{4}+\left(\dfrac{-1}{3}\right)-\dfrac{5}{18}\)

\(=\dfrac{3}{4}+\left(\dfrac{-6}{18}\right)-\dfrac{5}{18}\)

\(=\dfrac{3}{4}+\left(\dfrac{-11}{18}\right)\)

\(=\dfrac{27}{36}+\left(\dfrac{-22}{36}\right)=-\dfrac{5}{36}\)

\(=\dfrac{3}{4}-\dfrac{1}{3}-\dfrac{5}{18}=\dfrac{16}{12}-\dfrac{4}{12}-\dfrac{5}{18}=1-\dfrac{5}{18}\)

\(=\dfrac{18}{18}-\dfrac{5}{18}=\dfrac{13}{18}\)

`4 / 15 . 1 / 3 . 15 / 20`

`= [ 4 . 1 . 15 ] / [ 15 . 3 . 20 ]`

`= [ 4 . 1 . 15 ] / [ 15 . 3 . 4 . 5 ]`

`= 1 / [ 3 . 5 ]`

`= 1 / 15`

\(=\left(\dfrac{4}{15}.\dfrac{15}{20}\right).\dfrac{1}{3}=\dfrac{60}{300}.\dfrac{1}{3}=\dfrac{60}{900}=\dfrac{1}{15}\)

\(=\dfrac{4.1.15}{15.3.5.4}=\dfrac{1}{3.5}=\dfrac{1}{15}\)

a) (-124) + 24 = -100
b) 37. 78 + 37. 22
=  37 . ( 78 + 22 )
=  37 . 100
= 3700

\(a) (-124) + 24 = -100 b) 37. 78 + 37. 22 = 37 . ( 78 + 22 ) = 37 . 100 = 3700\)

a) (- 124) + 24                                          b) 37 . 78 + 37 . 22

= - ( 124 - 24)                                              =37 . ( 78 + 22)

= - 100                                                        =37 . 100 

                                                                    3700

a) \(26+150+74=\left(26+74\right)+150=100+150=250\).

b) \(35.46+54.35=35.\left(46+54\right)=35.100=3500\).

c) \(\left(-31\right)+\left[20-\left(7-4\right)^2\right]=\left(-31\right)+20-3^2=\left[\left(-31\right)-9\right]+20=-40+20=-20\)

d) Ta có: \(-8+\left(-14\right)+34+\left(-12\right)\)

\(=-8-14+34-12\)

\(=-20+20\)

\(=-0\)

e) Ta có: \(\left(-7\right)+\left(-20\right)+57+\left(-30\right)\)

\(=\left(-7+57\right)+\left(-20-30\right)\)

\(=50-50=0\)

f) Ta có: \(300-\left(-180\right)-120-42\)

\(=300+180-120-42\)

\(=258+60=318\)

d, Ta có : \(\left(-8\right)+\left(-14\right)+34+\left(-12\right)\)

\(=-\left(8+12\right)+34-14=-20+20=0\)

e, Ta có : \(\left(-7\right)+\left(-20\right)+57+\left(-30\right)\)

\(=-\left(30+20\right)+57-7=-50+50=0\)

f, Ta có : \(300-\left(-180\right)-120-42=318\)

d,=-8-14+34-12=(-8+34)-(14+12)

=26-26=0

e,=-7-20+57-30=(-7+57)-(20+30)

=50-50=0

f,=300+180-120-42=300+40-42=298

\(a.36+15+64\\ =\left(36+64\right)+15\\ =100+15\\ =115\\ b.12\cdot36+12\cdot64\\ =12\cdot\left(36+64\right)\\ =12\cdot100\\ =1200\\ c.\left(3^2+2^3\cdot5\right):7\\ =\left(9+8\cdot5\right):7\\ =\left(9+40\right):7\\ =49:7\\ =7\)\(\)

\(a,36+15+64\)

\(=\left(36+64\right)+15=100+15\)

\(=115\)

\(b,12.36+12.64\)

\(=12.\left(36+64\right)=12.100\)

\(=1200\)

\(c,\left(3^2+2^3.5\right):7\)

=\(\left(9+8.5\right):7\)

\(=49:7=7\)

a.36+15+64

=(36+64)+15

=100+15

=115

b.12.36+12.64

=12.(36+64)

=12.100

=1200

c.(3^2+2^3.5):7

=(9+8.5):7

=(9+40):7

49:7

=7

a,17.131+17.169

= 17 . (131 + 169)

= 17 . 300

= 5100

b,5⁶:5³+2³.2²

= 5³ + 2⁵

= 125 + 32

= 157

# HOK TỐT #