Bài 1: Tính:
a,(-8)×25×(-2)×4×(-5)×125
b,19×25+9×95+19×30
c,(-48)+48×(-78)+48×(-21)
d,13×(25+22)-3(17+18)
e,29×(19-13)-19×(29-13)
f,17×(-57)-23×37-46×(-37)
g,(-37-17)×(-9)+37×(-9-11)
h,(-25)×(75+45)-75×(45-25)
Bài 2:Tìm x thuộc Z:
a,(x+3)×(x-4)=0
b,(x-1)×(x-3)=0
Đáp án:
Giải thích các bước giải:
Bài 1: Tính:
a,(-8) × 25 × (-2) × 4 × (-5) × 125
=[(-2) × (-5)]× (25 × 4) × [(-8) × 125]
=10 × 100 × (-1000)
= (-1000000)
b,19 × 25 + 9 × 95 + 19 × 30
=19 × 25 + 9 × 5 × 19+ 19 × 30
=19 × 25 + 45 × 19+ 19 × 30
=19 × (25 + 45 + 30)
=19 × 100
=1900
c,(-48) + 48 × (-78) + 48 × (-21)
=(-1) × 48+ 48 × (-78) + 48 × (-21)
=(-1 – 78 – 21) × 48
=(-100) × 48
=(-4800)
d,13 × (25 + 22) – 3 × (17 + 18)
=13 × 47 – 3 × 35
=611 – 105
=506
e,29 × (19 – 13) – 19 × (29 – 13)
=29 × 19 – 29 × 13 – 19 × 29 + 19 × 13
=(29 × 19 – 19 × 29) + (19 × 13 – 29 × 13)
=0 + 13 × (19 – 29)
=13 × (-10)
=(-130)
f,17 × (-57) – 23 × 37 – 46 × (-37)
=(-969) – 851 – (-1702)
=(-969) – 851 + 1702
=(-118)
g,(-37 – 17) × (-9) + 37 × (-9 – 11)
=(-54)× (-9) + 37 × (-20)
=486 + (-740)
=486 – 740
=(-254)
h,(-25) × (75 + 45) – 75 × (45 – 25)
=(-25) × 120 – 75 × 20
=(-3000) – 1500
=(-4500)
Bài 2:Tìm x thuộc Z:
a,(x + 3) × (x – 4)=0
⇔\(\left[ \begin{array}{l}x + 3=0\\x – 4=0\end{array} \right.\)
⇔\(\left[ \begin{array}{l}x =-3\\x =4\end{array} \right.\)
Vậy x ∈ {-3;4} (tmđk x ∈ Z)
b,(x – 1) × (x – 3)=0
⇔\(\left[ \begin{array}{l}x – 1=0\\x – 3=0\end{array} \right.\)
⇔\(\left[ \begin{array}{l}x =1\\x =3\end{array} \right.\)
Vậy x ∈ {1;3} (tmđk x ∈ Z)
Bài 1: Tính:
a, (-8) × 25 × (-2) × 4 × (-5) × 125
= (-8 x 125) x (25 x 4) x [-2 x (-5)]
= -1000 x 100 x 10
= -1000000
b,19 × 25 + 9 × 95 + 19 × 30
= 19 x (25 + 30) + 9 x 95
= 19 x 55 + 9 x 95
= 1045 + 855
= 1900
c, (-48) + 48 × (-78) + 48 × (-21)
= 48 x (-1 – 78 – 21)
= 48 x (-100)
= -4800
d, 13 × (25 + 22) – 3 x (17 + 18)
= 13 x 47 – 3 x 35
= 611 – 105
= 506
e, 29 × (19 – 13) – 19 × (29 – 13)
= 29 x 6 – 19 x 16
= 174 – 304
= -130
f, 17 × (-57) – 23 × 37 – 46 × (-37)
= -969 – 851 + 1702
= -118
g, (-37 – 17) × (-9) + 37 × (-9 – 11)
= -54 x (-9) + 37 x (-20)
= 486 – 740
= -254
h, (-25) × (75 + 45) – 75 × (45 – 25)
= -25 x 120 – 75 x 20
= -3000 – 1500
= -4500
Bài 2: Tìm x thuộc Z:
a, (x + 3) × (x – 4) = 0
\(\left[ \begin{array}{l}x+3=0\\x-4=0\end{array} \right.\)
\(\left[ \begin{array}{l}x=0\\x=4\end{array} \right.\)
Vậy x = 0 hoặc x = 4
b, (x – 1) × (x – 3) = 0
\(\left[ \begin{array}{l}x-1=0\\x-3=0\end{array} \right.\)
\(\left[ \begin{array}{l}x=1\\x=3\end{array} \right.\)
Vậy x = 1 hoặc x = 3