Tools:
1, the method of addition, subtraction, multiplication and division according to the relationship between parts.
Addition: A+B = C
Appendix+Appendix = Sum
A = C — B
One addend = sum-another addend
Subtraction: X-Y = Z
Negative-negative = difference
X = Y + Z
Negative = negative+difference
Y = X - Z
Subtraction = minuend-difference
Multiplication: A × B = C
Factor × factor = product
A = C ÷ B
One factor = product ÷ another factor
Division: X ÷ Y = Z
Dividend = quotient
X = Y × Z
Dividend = divisor × quotient
Y = X ÷ Z
Divider = Divider
2. According to the properties of the equation
Add or subtract the same number from both sides of the L equation, and the equation still holds.
When both sides of the L equation are multiplied by a number or divided by a number that is not 0, the equation still holds.
For example, if X=5 holds, then X+2=5+2, X-3=5-3, X×2=5×2, and X÷2=5÷2 also holds.
3, the method of moving items.
Observe the following equation:
X +5 = 8 X - 4 = 5
X+5-5 = 8-5 X-4 +4 = 5+4
X = 8-5 X = 5+4
X×5 = 10 X ÷4 = 2
X×5÷5 = 10÷5 X÷4×4 = 2×4
X = 10÷5 X = 2×4
Moving an item in an equation from one side of the equation to the other is called moving the item; When moving objects, you should change the operation symbol, that is, adding one to the other side becomes subtracting one, subtracting one to the other side becomes adding one, multiplying one to the other side becomes dividing one, and dividing one to the other side becomes multiplying one.
Skills: overall thinking, moving items and merging ideas.
Basic type: X+A=B X-A=B A -X =B
X = B-A X = B+A A–B = X
x = A–B
X×A=B X÷A=B A÷X=B
X = B÷A X = B×A÷B = X
X=A÷B
For example: 20x+20 = 80
Take 20x as a whole and shift +20 to the right to become -20.
(Transfer item) 20x=80-20
(Consolidated) 20x=60
X = 60÷ 20
X = 3
Such as: 30-2X= 10
30- 10 =20X
20X= 30- 10
20X=20
X=20÷20
X= 10