Áp dụng tính chất \(a\left(b-c\right)=ab-ac\) , điền số thích hợp vào chỗ trống :
a) \(.......\left(-13\right)+8.\left(-13\right)=\left(-7+8\right).\left(-13\right)=.......\)
b) \(\left(-5\right)\left(-4-......\right)=\left(-5\right).\left(-4\right)-\left(-5\right).\left(-14\right)=.......\)
Điền số thích hợp vào chỗ trống (....)
a) \(\left(-5\right).\left(-4\right)+\left(-5\right).14=\left(-5\right).\left[\left(-4\right)+....\right]=.....\)
b) \(3.\left(....+8\right)=13.\left(-3\right)+13.......=65\)
a) (-5) . (-4) + (-5) . 14 = (-5 ) . [ (-4) + 14 ] = -50
b ) 3 . ( 5 + 8 ) = 13 . ( -3 ) + 13 . 8 = 65
Điền dấu ">", "<" thích hợp vào chỗ trống :
a) \(\left(-2\right)+\left(-5\right)......\left(-5\right)\)
b) \(\left(-10\right)......\left(-3\right)+\left(-8\right)\)
a) (-2)+ (-5) = -7
Vì: -7< -5
=> (-2)+ (-5) < -7
b) (-3)+ (-8)= -11
Vì: (-10) > (-11)
=> -10> (-3)+ (-8)
a) \(\left(-2\right)+\left(-5\right)..........\left(-5\right)\)
\(\left(-7\right)< \left(-5\right)\)
Vậy \(\left(-2\right)+\left(-5\right)< \left(-5\right)\)
b) \(\left(-10\right)...........\left(-3\right)+\left(-8\right)\)
\(\left(-10\right)>\left(-11\right)\)
Vậy \(\left(-10\right)>\left(-3\right)+\left(-8\right)\)
Tính một cách hợp lí:
a) \(\left(-16\right).\left(-7\right).5;\) b) \(11.\left(-12\right)+11.\left(-18\right);\)
c) \(87.\left(-19\right)-37.\left(-19\right);\) d) \(41.81.\left(-451\right).0.\)
a) (- 16) . (- 7) . 5 = [(- 16) . 5] . (- 7) = 560.
b) 11 . (- 12) + 11 . (- 18) = 11 . [(- 12) + (- 18)] = 11 . [- (12 + 18)] = 11 . (- 30) = - 330.
c) 87 . (- 19) – 37 . (- 19) = (- 19) . (87 – 37) = (- 19) . 50 = - 950.
d) 41 . 81 . (- 451) . 0 = 0.
a) (- 16) . (- 7) . 5 = [(- 16) . 5] . (- 7) = 560.
b) 11 . (- 12) + 11 . (- 18) = 11 . [(- 12) + (- 18)] = 11 . [- (12 + 18)] = 11 . (- 30) = - 330.
c) 87 . (- 19) – 37 . (- 19) = (- 19) . (87 – 37) = (- 19) . 50 = - 950.
d) 41 . 81 . (- 451) . 0 = 0.
a) (-16).(-7).5
=16.7.5 = 2.8.7.5
=(2.5).(8.7) = 56 . 10 =560
b) 11 . (-12) + 11.(-18)
=11 . (-12 -18)
=11.(-20) = -220
c) 87.(-19) - 37 .(-19)
=(-87).19 + 37.19
=19 . (-87+37)
=19.(-50)
= -950
d) 41.81.(-451).0
= (mọi số nhân 0 đều bằng 0)
Điền dấu > , < vào chỗ trống :
a) \(\left(-6\right)+\left(-3\right).....\left(-6\right)\)
b) \(\left(-9\right)+\left(-12\right).....\left(-20\right)\)
a, \(\left(-6\right)+\left(-3\right).....\left(-6\right)\)
\(\left(-9\right)< \left(-6\right)\)
Vậy \(\left(-6\right)+\left(-3\right)< \left(-6\right)\)
b,\(\left(-9\right)+\left(-12\right)....\left(-20\right)\)
\(\left(-21\right)< \left(-20\right)\)
\(\Rightarrow\left(-9\right)+\left(-12\right)< \left(-20\right)\)
\(\text{Thực hiện các phép tính sau một cách hợp lý:}\)
\(a\)) \(\left(10^2+11^2+12^2\right):\left(13^2+14^2\right)\)
\(b\)) \(1.2.3...9-1.2.3...8-1.2.3...7.8^2\)
\(c\)) \(\dfrac{\left(3.4.2^{16}\right)^2}{11.2^{13}.4^{11}-16^9}\)
\(d\)) \(1152-\left(374+1152\right)+\left(-65+374\right)\)
\(e\)) \(13-12+11+10-9+8-7-6+5-4+3+2-1\)
Tính :
a) \(5+\left(-7\right)+9+\left(-11\right)+13+\left(-15\right)\)
b) \(\left(-6\right)+8+\left(-10\right)+12+\left(-14\right)+16\)
a)
\(5+\left(-7\right)+9+\left(-11\right)+13+\left(-15\right)\)
\(=\left[5+\left(-7\right)\right]+\left[9+\left(-11\right)\right]+\left[13+\left(-15\right)\right]\)
\(=\left(-2\right)+\left(-2\right)+\left(-2\right)=-6\)
b)
\(\left(-6\right)+8+\left(-10\right)+12+\left(-14\right)+16\)
\(=\left[\left(-6\right)+8\right]+\left[\left(-10\right)+12\right]+\left[\left(-14\right)+16\right]\)
\(=2+2+2=6\)
Tính hợp lý:
\(A=\dfrac{7}{12}+\dfrac{5}{12}:6-\dfrac{11}{36}\) \(B=\left(\dfrac{4}{5}+\dfrac{1}{2}\right):\left(\dfrac{3}{13}-\dfrac{8}{13}\right)\)
\(C=\left(\dfrac{2}{3}-\dfrac{1}{4}+\dfrac{5}{11}\right):\left(\dfrac{5}{12}+1-\dfrac{7}{11}\right)\)
a: \(A=\dfrac{7}{12}+\dfrac{5}{72}-\dfrac{11}{36}=\dfrac{42}{72}+\dfrac{5}{72}-\dfrac{22}{72}=\dfrac{25}{72}\)
b: \(B=\dfrac{8+5}{10}:\dfrac{-5}{13}=\dfrac{13}{10}\cdot\dfrac{13}{-5}=-\dfrac{169}{100}\)
c: \(C=\left(\dfrac{88}{132}-\dfrac{33}{132}+\dfrac{60}{132}\right):\left(\dfrac{55}{132}+\dfrac{132}{132}-\dfrac{84}{132}\right)\)
\(=\dfrac{88-33+60}{55+132-84}=\dfrac{115}{103}\)
\(8x^2-5x-22=\left(ax+11\right)\left(bx-2\right)\)
\(\Leftrightarrow\left(8x+11\right)\left(x-2\right)=\left(ax+11\right)\left(bx-2\right)\)
\(\Leftrightarrow\left\{{}\begin{matrix}a=8\\b=1\end{matrix}\right.\Rightarrow a-b=8-1=7\)
