a ) x = − 3 4 + 4 5 ⇔ x = 1 20 b ) x = − 4 9 : 2 , 5 ⇔ x = − 8 45 c ) 3 , 5 − 2 x = 1 7 : 2 3 7 ⇔ 3 , 5 − 2 x = 1 17 ⇔ 2 x = 3 , 5 − 1 17 ⇔ 2 x = 117 34 ⇔ x = 117 34 : 2 = 117 68

a: =-100-317=-417

a: =-100-317=-417

a: \(35\left(45-237\right)-45\left(35-237\right)\)

\(=35\cdot45-35\cdot237-45\cdot35+45\cdot237\)

\(=45\cdot237-35\cdot237=237\cdot10=2370\)

b: \(-48+48\cdot\left(-78\right)+48\cdot\left(-21\right)\)

\(=-48\left(1+78+21\right)\)

\(=-48\cdot100=-4800\)

125-30-x-125=x-237-8+237

-30-x=x-8

=> -30=2x-8

=> x=-11

125-(30+x+125)=(x-237).[8+(-237)]

125-(30+x+125)=(x-237)×(-229)

125-(30+x+125)=x-237×(-229)

125-(30+x+125)=x-(-54273)

125-(30+x+125)=x+54273

125-30+x+125=x+54273

125-39+x=x+54273-125

125-39+x=x+54148

125-x=x+54148-39

125-x=x+54109

125-1x=1x+54109

125-1x=0

1x=125-0

1x=125

x=125÷1

x=125

dung nhung dai

21 * 49

= 21 * (50 - 1)

= 21 * 50 - 21 * 1

= 1050 - 21

= 1029

Câu a:

- 237 - (- 237 + 95) + 195

= - 237 + 237 - 95 + 195

= 0 - 95 + 195

= - 95 + 195

= 100

b,-362-[-(362-97)-17]

= - 362 + 362 - 97 + 17

= 0 - 97 + 17

= -97 + 17

= - 80

Bài giải

Ta có: \(\frac{49+\left(-49\right).\left(-2\right)}{7.21}\)

= \(\frac{49.1+49.2}{7.21}\)

= \(\frac{49.\left(1+2\right)}{7.21}\)

= \(\frac{49.3}{7.21}\)

= \(\frac{7.7.3}{7.7.3}\)

= \(1\)