Giải thích các bước giải:
BÀI 1
a: 3/5-(-7/10)-(13/-28) b: 3/4+(-1/3)-5/18
=247/140 =27/36+(-12/36)-10/36
=5/36
c: 3/14-(-5/-8)+(-1/2) d:1/2+(-1/3)+1/4-3/6
=12/56-35/56+(-28/56) =6/12+(-4/12)+3/12-6/12 =-51/56 =-1/12 BÀI 2
a: x +3/4=-5/9 b: -1/3+x=5/6
⇔x=-5/9-3/4 ⇔x=5/6+1/3
⇔x=-20/36-27/36 ⇔x=5/6+2/6
⇔x=-47/36 ⇔x=7/6
BÀI 3
a: 11/12-(2/5+x )=2/3 b: 2x.(x-1/7)=0
⇔-2/5-x =2/3-11/12 ⇔x-1/7=0
⇔-2/5-x=-1/4 ⇔x=1/7
⇔x =3/20
c: 3/4+1/4÷x=2/5
⇔1/4÷x=2/5-3/4
⇔1/4÷x=-7/20
⇔x=1/4÷(-7/20)
⇔x=1/4×(-20/7)
⇔x=-5/7
BÀI 4
a: (-3.8)+⊂(-5.7)+(+3.8)⊃ b: 31.4+4.6+(-18)
=(-3.8)+⊂-1.9⊃ =18
=-3.8-1.9
=-5/7
c: (-9.6) +4.5-1.5
=-6.6
d: 12345.4321 × 2468.91011 + 12345.4321 × (- 2468.91011)
=(2468.91011 -2468.91011) ×(12345.4321 +12345.4321)
= 0 × ( 12345.4321 + 12345.4321)
= 0
BÀI 5
M=a +2ab -b N=a÷2 - 2÷b
=1.5 +2×1.5×(-0.75) =1.5÷2 - 2÷(-0.75)
=1.5+(-2.25) =3/2÷2 -2÷( -3/4)
=-0.75 =3/4-(-8/3)
=41/12
P=(-2)÷a²-b-2/3
=(-2)÷(1.5)²-(-0.75)-2/3
=(-2)÷9/4 - (-3/4) -2/3
=-8/9 - (-3/4) - 2/3
= -29/36
BÀI6
a: f(5)=12/5 f(-3)=12/-3=-4
b:
x -6 -4 2 12
y -2 -3 6 1
