14-∣-30∣+(-10)-(-86)=
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8. Find the value of 14 x 14 + 2 x 14 x 86 + 86 x 86.
\(=\left(14\times3\right)+\left(86\times3\right)+2\)
\(=42+258+2\)
\(=300+2\)
\(=302\)
14 x 14 + 2 x 14 x 86 + 86 x 86
= 14 x 14 + 14 x 86 + 14 x 86 + 86 x 86
= 14 x ( 14 + 86 ) + 86 x ( 14 + 86 )
= 14 x 100 + 86 x 100
= 100 x ( 14 + 86 )
= 100 x 100
= 10000
34*86+51*86+85*14
=86*(34+51)+85*14
=86*85+85*14
=85*(86+14)
=85*100
=8500
\(34\cdot86+51\cdot86+85\cdot14\)
\(=(34+51)\cdot(86+14)\)
\(=85\cdot100=8500\)
Chúc bạn học tốt
7) \(\frac{x+25}{75}+\frac{x+30}{70}=\frac{x+35}{65}+\frac{x+40}{60}\)
\(\Leftrightarrow\)\(\frac{x+25}{75}+1+\frac{x+30}{70}+1=\frac{x+36}{65}+1+\frac{x+40}{60}+1\)
\(\Leftrightarrow\)\(\frac{x+100}{75}+\frac{x+100}{70}=\frac{x+100}{65}+\frac{x+100}{60}\)
\(\Leftrightarrow\)\(\left(x+100\right)\left(\frac{1}{75}+\frac{1}{70}-\frac{1}{65}-\frac{1}{60}\right)=0\)
\(\Leftrightarrow\)\(x+100=0\) (vì 1/75 + 1/70 - 1/65 - 1/60 \(\ne\)0)
\(\Leftrightarrow\)\(x=-100\)
Vậy.....
7) \(\frac{x+25}{75}+\frac{x+30}{70}=\frac{x+35}{65}+\frac{x+40}{60}\)
\(\Leftrightarrow\)\(\frac{x+25}{75}+1+\frac{x+30}{70}+1=\frac{x+35}{65}+1+\frac{x+40}{60}+1\)
\(\Leftrightarrow\)\(\frac{x+100}{75}+\frac{x+100}{70}=\frac{x+100}{65}+\frac{x+100}{60}\)
\(\Leftrightarrow\)\(\left(x+100\right)\left(\frac{1}{75}+\frac{1}{70}-\frac{1}{65}-\frac{1}{60}\right)=0\)
\(\Leftrightarrow\)\(x+100=0\) (1/75 + 1/70 - 1/65 - 1/60 \(\ne\)0)
\(\Leftrightarrow\)\(x=-100\)
Vậy...
a) 27 × 10 = 270; 72 × 100 = 7200; 14 × 1000 = 14000
86 × 10 = 860; 103 × 10 = 10300; 452 × 1000 = 452000
358 × 10 = 3580; 1977 × 100 = 197700; 300 × 1000 = 300000
b) 80 :10 = 8; 400 : 100 = 4 ;6000 : 1000 = 6
300 : 10 = 30; 4000 : 100 = 40 ; 60000 : 1000 = 60
2000 :10 = 200; 40000 :100 = 400 ;600000 : 1000 = 600
c) 64 × 10 = 640; 32 × 100 = 3200; 95 × 1000 = 95000
640 : 10 = 64; 3200 : 100 = 32; 95000 : 1000 = 95
=14-30-10+86
=100+20
=120
TL :
=14-30-10+86
=100+20
=120