Question

Tìm x , biết : 

a) 14-5+x=30

b) 45-(3+x)=14

c)18+(-3+x)-(44-x)=55

d) (x-45).27=0

e) 25.(42-x)=23

g) 156-(x+61)=82

h) 70-5(x-3)=45

i) | x+2 | = -(-8)+|-7|

k) (x-2)² = 30-2.7

Answer 1

\(a,14-5+x=30\)

\(\Rightarrow9+x=30\Rightarrow x=30-9\)

\(\Rightarrow x=21\)

\(b,45-\left(3+x\right)=14\)

\(\Rightarrow3+x=45-14\)

\(\Rightarrow3+x=31\Rightarrow x=31-3\)

\(\Rightarrow x=28\)

\(c,18+\left(-3+x\right)-\left(44-x\right)=55\)

\(\Rightarrow18-3+x-44+x=55\)

\(\Rightarrow2x-29=55\Rightarrow2x=55+29\)

\(\Rightarrow2x=84\Rightarrow x=84:2\)

\(\Rightarrow x=42\)

\(d,\left(x-45\right).27=0\)

\(\Rightarrow x-45=0\Rightarrow x=45\)

Answer 2

\(a,14-5+x=30\)

\(\Rightarrow9+x=30\)

\(\Rightarrow x=30-9=21\)

Answer 3

\(b,45-\left(3+x\right)=14\)

\(\Rightarrow3+x=45-14=31\)

\(\Rightarrow x=31-3=28\)

Answer 4

\(c,18+\left(-3+x\right)-\left(44-x\right)=55\)

\(\Rightarrow18-3+x-44+x=55\)

\(\Rightarrow2x-29=55\)

\(\Rightarrow2x=55+29=84\)

\(\Rightarrow x=84:2=42\)

Answer 5

a) (14 - 5 ) + x = 30

          9      + x = 30

                     x = 30 -9

                     x=      21

Answer 6

\(e,25.\left(42-x\right)=23\)

\(\Rightarrow42-x=23:25\Rightarrow42-x=\frac{23}{25}\)

\(\Rightarrow x=42-\frac{23}{25}\Rightarrow x=\frac{1027}{25}\)

\(g,156-\left(x+61\right)=82\)

\(\Rightarrow x+61=156-82\)

\(\Rightarrow x+61=74\Rightarrow x=13\)

\(h,70-5\left(x-3\right)=45\)

\(\Rightarrow5\left(x-3\right)=25\)

\(\Rightarrow x-3=5\Rightarrow x=8\)

\(i,\left|x+2\right|=-\left(-8\right)+\left|-7\right|\)

\(\Rightarrow\left|x+2\right|=8+7\Rightarrow\left|x+2\right|=15\)

\(\Rightarrow x+2=\pm15\Rightarrow x=-17;13\)

\(k,\left(x-2\right)^2=30-2.7\)

\(\Rightarrow\left(x-2\right)^2=16\)

\(\Rightarrow\left(x-2\right)^2=\left(\pm4\right)^2\)

\(\Rightarrow x-2=\pm4\Rightarrow x=-2;6\)