Bài 3: 

a: \(=-8\left(72+19-1\right)=-8\cdot90-720\)

b: \(=-27\left(1011-12-1\right)=-27\cdot998=-26946\)

c: \(=17\cdot\left[29+111\right]+29\cdot\left(-17\right)\)

\(=17\left(29+111-29\right)=17\cdot111=1887\)

d: \(=43\cdot\left(-1\right)+40=-43+40=-3\)

Đặt a=315; b=651

\(A=2\frac{1}{315}\cdot\frac{1}{651}-\frac{1}{105}\cdot3\frac{650}{651}-\frac{4}{315\cdot651}+\frac{4}{105}\)

\(=\left(2+\frac{1}{a}\right)\cdot\frac{1}{b}-\frac{3}{a}\cdot\left(3+\frac{b-1}{b}\right)-\frac{4}{ab}+\frac{12}{a}\)

\(=\frac{2a+1}{a}\cdot\frac{1}{b}-\frac{3}{a}\cdot\frac{3b+b-1}{b}-\frac{4}{ab}+\frac{12b}{ab}\)

\(=\frac{2a+1-3\left(4b-1\right)-4+12b}{ab}=\frac{2a-3-12b+3+12b}{ab}=\frac{2a}{ab}=\frac{2}{b}\)

=2/651

Đặt a=315; b=651

\(A=2\frac{1}{315}\cdot\frac{1}{651}-\frac{1}{105}\cdot3\frac{650}{651}-\frac{4}{315\cdot651}+\frac{4}{105}\)

\(=\left(2+\frac{1}{a}\right)\cdot\frac{1}{b}-\frac{3}{a}\cdot\left(3+\frac{b-1}{b}\right)-\frac{4}{ab}+\frac{12}{a}\)

\(=\frac{2a+1}{a}\cdot\frac{1}{b}-\frac{3}{a}\cdot\frac{3b+b-1}{b}-\frac{4}{ab}+\frac{12b}{ab}\)

\(=\frac{2a+1-3\left(4b-1\right)-4+12b}{ab}=\frac{2a-3-12b+3+12b}{ab}=\frac{2a}{ab}=\frac{2}{b}\)

=2/651

25 + 115 - 315 + 105 = ( 25 + 105) + (115 - 315) 

= 130 -200

= -70

sai rồi trên công thì dười cũng phải công chứ

a.

\(-\left(-315\right)+\left(-115\right)-105+25=315-115-105+25=120\)

b.

\(888-\left(-333\right)-222+70=888+333-222+70=1069\)

c.

\(25\times\left(32+47\right)-32\times\left(25+47\right)=25\times32+25\times47-32\times25-32\times47=-47\times\left(32-25\right)=-47\times7=-329\)

Đặt 1/315=a      ;  1/651=b

2+a*b-3a(4-b)-4ab+12a

=2b=2*1/651=2/651

\(a.\)

\(-\left(-315\right)+\left(-115\right)-105+25\)

\(315-115-105+25\)

\(=215\)

\(b.\)

\(888-\left(-333\right)-222+111\)

\(=888+333-222+111\)

\(=1110\)

\(c.\)

\(-97-15+44-35-12+98\)

\(=-17\)

bấm máy tính là ra mà

ko bt cách làm

5

[ ( 9 - 18 ) + ( -17 ) ] + ( -15 )

= [ ( -9 ) + ( -17 ) ] + ( -15 )

= ( -26 ) + ( -15 )

= -41

666 - ( -442 ) - 100 - 88

= 666 + 442 - 100 - 88

= 1108 - 100 - 88

= 1008 - 88

= 920

- ( -315 ) + ( -115 ) - 105 + 25

= 315 + ( -115 ) - 105 + 25

= 200 - 105 + 25

= 95 + 25

= 120

888 - ( -333 ) - 222 + 70

= 888 + 333 - 222 + 70

= 1221 - 222 + 70

= 999 + 70

= 1069

A=-64.125+25.(-8)²-600

=-64.125+25.64-600

=25.64-64.125-600

=(25-125).64-600

=(-100).64-600

=-6400-600=-7000

B=315-115-(105-25)

=200-80=120

K=1351-875-125+149

=(1351+149)-(875+125)

=1500-1000=500