3 (x-2.1) = 8.4

3 (x-2.1) = 8.4

3（x-2.1）=8.4
x-2.1=8.4÷3
x-2.1=2.8
x=2.1+2.8
x=4.9

Solving equation (1 / 4) ^ (x + 1) - 3 (1 / 2) ^ x + 8 = 0

Let a = (1 / 2) ^ x
Then (1 / 4) ^ x = A & # 178;
So a & # 178; * 1 / 4-3a + 8 = 0
a²-12a+32=0
(a-4)(a-8)=0
a=4,a=8
(1/2)^x=2^(-x)=4
-x=2
x=-2
Similarly, if (1 / 2) ^ x = 8, then x = - 3
So x = - 2, x = - 3

How to calculate 0.386 * (4.82 + 5.7 + 5.1 + 2.3) / 3.86? There are 9 * 3-1.7 = 13.4 to solve the equation
It is 9 × 3-1.7x = 13.4

0.386*(4.82+5.7+5.1+2.3)/3.86
= (4.82+5.7+5.1+2.3)/10
= (4.82+5.1+5.7+2.3)/10
= (9.92+8)/10
= 17.92/10
= 1.792
9*3-1.7=13.4

3.6 divided by 3 / 2 = x + 2 / 1 (x-1) = 9 (solving equation) 4 / 1:6 / 1 = (reduction ratio)

2.4=x+2
x=0.4
2：3

2.4 divided by (x-13.5) = 3

2.4 divided by (x-13.5) = 3
x-13.5=2.4÷3
x-13.5=0.8
x=14.3

If the solutions of the equation 5x + 12 = 4A of X are all negative, then the value range of a is ()
A. a＞3B. a＜-3C. a＜3D. a＞-3

Solve the equation about X: x = 4A − 125, according to the meaning: 4A − 125 < 0, the solution is a < 3

If the speed of the ship in still water is 23 km / h and the current speed is 3 km / h, and the distance between a and B is s km, it will take a total of ()
A. 2S / 23 hours B. (2S / 23 + 2S / 3) hours
C. (s / 26 + S / 20) hours b.2s/13 hours

Choose C for this question
Travel time along the water = s / (23 + 3) = s / 26
Time of going against the water = s / (23-3) = s / 20

To check the correct format of the equation of one degree with one variable, we need the kind in mathematics books and examples

Glad to answer your question!
Basic steps of checking calculation
1. Will x=____ Substituting into the original equation
2. Left=_________ Right=_________
3. Left = right
4. So, X=____ Is the solution of the original equation
Example: x + 35 = 75.8 368.5-x = 21.6
6X=7.5 1.55÷X=0.5 X÷4=3.48
---------------------------------------------------------------
X+35=75.8
X=75.8-35
X=40.8
Test: substitute x = 40.8 into the original equation
Left = 40.5 + 30 = 75.8, right = 75.8
Left = right
So, x = 40.8 is the solution of the original equation
368.5-X=21.6
X=368.5-21.6
X=346.9
Test: substitute x = 346.9 into the original equation
Left = 368.5-346.9 = 21.6, right = 21.6
Left = right
Therefore, x = 346.9 is the solution of the original equation
6X=7.5
X=7.5÷6
X=1.25
Test: substitute x = 1.25 into the original equation
Left = 6 × 1.25 = 7.5, right = 7.5
Left = right
So, x = 1.25 is the solution of the original equation
1.55÷X=0.5
X=1.55÷0.5
X=3.1
Test: substitute x = 3.1 into the original equation
Left = 1.55 △ 3.1 = 0.5, right = 0.5
Left = right
So, x = 3.1 is the solution of the original equation
X÷4=3.48
X=3.48×4
X=13.92
Test: substitute x = 13.92 into the original equation
Left = 13.92 △ 4 = 3.48, right = 3.48
Left = right
So, x = 13.92 is the solution of the original equation
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The checking calculation of one variable linear equation in grade one of junior high school, x = 1, equation, 5x-3 = 4x + 2, please be more detailed
In words

Checking calculation: ∵ x = 1 is the solution of equation 5x-3 = 4x + 2
The equation of x = 1 is obtained
5×1-3=4×1+2
2=6
∵2≠6
The left is not equal to the right
X = 1 is not the solution of this equation

Calculation of linear equation with one variable
2X-4 of 2-3 = - X-7 of 6
2 / 3x + 1 = X-1
0.02x of 0.03 + 0.01-0.6x of 0.6 + 1 = 2

2-3 / 2X-4 = - 6 / X-7 shift: (- 2 / 3) x + X / 6 = - 7-2 + 4 merge similar items: - X / 2 = - 5 coefficient reduced to 1: x = 102 / 3x + 1 = X-1 shift: (3 / 2) x-x = - 1-1 merge similar items: X / 2 = - 2 coefficient reduced to 1: x = - 40.03 / 0.02x + 0.01-0.6 / 0.6x + 1 = 2 simplify: (2 /...)