The content of the first year of mathematics, what is the introduction of the content of the first y

Let's say it's A and B.

then a+b=50

a=50-b

400a+1200b=48000

So 400 (50-b) + 1200b = 4800020000-400b + 1200b = 48000800b = 28000

b=35a=50-b=15

Let's say it's b and c.

then b+c=50

b=50-c

1200b+1800c=48000

So 1200 (50-c) + 1800c = 4800060000-1200c + 1800c = 48000600c = -12000

c=-20 is not a negative number, so it is not true.

Let's say it's a and c.

then a+c=50

a=50-c

400a+1800c=48000

So 400 (50-c) + 1800c = 4800020000 - 400c + 1800c = 480001400c = 28000

c=20a=50-c=30

So it's A15, B35 or A30, C20.

Set up and buy A type X station, B type Y station, C type Z platform.

1。 x+y=50

400x+1200y=48000

2. x+z=50

400x+1800z=48000

3. y+z=50

1200y+1800z=48000

There should be two kinds of non-conformities that are excluded after solving.

The specific solution time relationship is not answered.

Is it ternary once?

Solution: Suppose A bought X units, B bought Y units, and C bought Z units.

400x+1200y+1800z=48000 is assumed to be a and b.

then a+b=50

a=50-b

400a+1200b=48000

So 400 (50-b) + 1200b = 4800020000-400b + 1200b = 48000800b = 28000

b=35 a=50-b=15

Let's say it's b and c.

then b+c=50

b=50-c

1200b+1800c=48000

So 1200 (50-c) + 1800c = 4800060000-1200c + 1800c = 48000600c = -12000

c=-20 is not a negative number, so it is not true.

Let's say it's a and c.

then a+c=50

a=50-c

400a+1800c=48000

So 400 (50-c) + 1800c = 4800020000 - 400c + 1800c = 480001400c = 28000

c=20 a=50-c=30

Column equations: 40oa+12oob+18o0c=4800

a+b+c=50

Each is equal to zero and solves the system of equations. The remaining two unknowns are available to see if there is an integer solution. When one of them is zero and the other two are integers, this problem is solved.

Rational numbers, integers, unary equations.

Chapter 1 Rational Numbers.

1 1 Positive and negative.

Reading & Thinking Use positive and negative numbers to express the allowable error of machining.

1 2 Rational numbers.

1 3 Addition and subtraction of rational numbers.

Experiment with** Fill in the magic square.

Reading and Thinking The Chinese were the first to use negative numbers.

1 4 Multiplication and division of rational numbers.

Observe and think about the mathematics of the flop.

1 5 Powers of rational numbers.

Math activities. Summary Review Question 1

Chapter 2 Addition and Subtraction of Whole Formulas.

2 1 Integer.

Reading & Thinking The conversation between the number 1 and the letter x.

2 2 Addition and subtraction of integers.

Information Technology Applications: Electronics** and Data Computing.

Math activities. Summary Review Question 2

Chapter 3 Unary Equations.

3 1 From Equation to Equation.

Read and think about the history of "equations".

3 2 Solving a Linear Equation (1) - Merging the Homogeneous Term and the Shift Term Experiment with ** Infinite Cyclic Fractional Fractions.

3 3 Solving a Univariate Equation (2) – Removing Parracks and Denominators 3 4 Practical Problems and Unary Linear Equations.

Math activities. Summary Review Question 3

Chapter 4 Preliminary Graphic Understanding.

4 1 Colorful graphics.

Read and Reflect on The Origins of Geometry.

4 2 Straight lines, rays, line segments.

Reading & Thinking Measurement of length.

4 3 corners.

4 4 Topic Learning Mathematical activity of designing and making a box-shaped packaging carton.

Summary Review Question 4

The main study in the first year of junior high school: rational numbers, addition and subtraction of integers, unary equations, and preliminary understanding of graphs.

Chapter 1 Rational Numbers.

Chapter 2 Addition and Subtraction of Whole Formulas.

Chapter 3 Unary Equations.

Chapter 4 Preliminary Graphic Understanding.

Algebraic and algebraic formulas and their mixed operations, Rational numbers and their operations, Scientific notation, integers and their operations, Unary equations, points, lines, angles and triangles in geometry.

Negative numbers and their operations, number lines, real number operations, congruent triangles.

1. Rational numbers: negative numbers, number lines, rational numbers, absolute values, size comparisons, 2. Operations on rational numbers: addition of rational numbers, subtraction of rational numbers, multiplication of rational numbers, division of rational numbers, multiplication of rational numbers, mixed operations, approximate numbers, scientific notation, 3. Real numbers: square roots, real numbers, irrational numbers, cubic roots, real number operations, 4. Algebraic formulas: use letters to represent numbers, algebraic formulas, algebraic values, integers, merging similar terms, addition and subtraction of integer formulas, 5. Unary Equations: Unary Linear Equations, The basic properties, solutions, and applications of equations, 6. Preliminary knowledge of graphics: geometric figures, line segments, rays, straight lines, length comparison, line segment and difference, angle and angle measurement, angle size comparison, angle sum difference, co-angle and complementary angle, and the intersection of straight lines.

Hello! In the first semester of junior high school, I mainly studied ——

Chapter 1 Rational Numbers.

Chapter 2 Addition and Subtraction of Whole Formulas.

Chapter 3 Unary Equations.

Chapter 4 Preliminary Geometry.

After a rolling defeat, the first salary after the half-bend is 300 + 50 (18-1) = 1150 yuan.

Solve the equation 300+50 (x-1)=2000

x = 35, that is, the monthly salary reaches 2,000 yuan after 35 months.

I usually don't work hard, and I crammed before the exam. I despise you.

b Because x+y represents the total amount, it represents the mixed amount.

Subtracting a negative number from a number is equal to adding the opposite of this negative number: 5-(-3)=5+3=8 A number minus another number is equal to the opposite of adding this number. Differents added:

26 + (-20) = 6 subtract from the same sign: 26-20 = 26 + (-20) = 6

One number minus another number is equal to the opposite number of adding this number. Addition of different signs: 26 + (-20) = 6 and subtraction of the same sign: 26-20 = 26 + (-20) = 6

A number minus a negative number is equal to the opposite number of the negative number: 5-(-3)=5+3=8 This seems to be the chapter of rational number operation The landlord can take a look at the definition in the book Combined with the example questions will understand Very simple As for which equations the landlord said are the addition of different numbers and the subtraction of the same sign What does this mean Can you ask.