I am very anxious about the math problem of the first year of junior high school, please help me sol

If you are in the first year of junior high school, you haven't learned binary equations yet.

That's all right. Let the length be a, then the width is (60-a) 4 then a+2x(60-a) 4=21+3x(60-a) 4a+(120-2a) 4=21+(180-3a) 44a+120-2a=84+180-3a

5a=144

a=then the width of the small rectangle is:(

The width of the large rectangle is: 21+

So the shaded part area is.

I can't vouch for the exact right calculation.

But the way is it, yes.

You said it was the first year of junior high school.

So it can be calculated like this.

I am a junior high school teacher.

I haven't learned binary equations yet.

Hopefully, this idea can help you a little.

Let the length of the small rectangle be x and the width be y

x+4y=66

The following formula is more obscure: the shaded part on the right side of the note is 21 is equal to the length of the rectangle minus 3 widths to get the width of the very narrow shaded part, plus 2 widths is equal to 21.

x-3y+2y=21 x-y=21

Solve the equation: y=9

x = 30, and then the shaded part is the area of the whole rectangle minus the nine lower rectangles.

Let the length of the small rectangle be a and the width be b, then according to the figure:

66＝4b＋a （1）

21＋3b＝a＋2b （2）

Solve the above equation to obtain:

a＝30b＝9

The width of the large rectangle is 21 3b 21 3 9 48, and the area of the large rectangle is 66 48 3168

The sum of the area of the small rectangle is 30 9 9 2430

The sum of the shadow area is 3168 2430 738

Let the length be x, the width be y, x+4y=66, x+2y=3x+21Solve this system of equations, and the shadow area can be found.

Three shades can be put together to form a rectangle, and the rest is easy.

The sign of ab is the same, i.e., the same positive or the same negative.

1-2x/3=3x+1/7-3

Multiply both sides of the equation by 21 at the same time to get.

7(1-2x)=3(3x+1)-3*21

7-14x=9x+3-63

23x=67

x=67/23

3 12x-(x-2) 3+1=0, then x=-1 7 brings x=-1 7 into the algebraic equation (3x-1) 4+(2x+1) 3, and the result is -120 7

Hope you're satisfied.

It is both positive or negative with b.

2.(1) Multiply both sides of the equation by 21 at the same time to get:

7（1-2x）=3（x+1）-63 17x=67 x=67/17

2）“2/3[1+（1+2x）/4]”？

3.Multiply the first equation by 3 to get: 36x-x+2+3=0 so x=-1 7 (minus seventh).

The second algebraic simplification: (17x+1) 12 Bring in the value of x, resulting in -5 42 (minus 5/42).

It is both positive or negative with b.

1.The condition for this to be true is that the symbols of the two numbers must be the same.

Knife holder x blade is sold and 50x

A: Profit of each razor Total profit = 8400 * yuan B: Profit is twice that of A = 4200 * 2 = 8400 yuan The knife holder loses 4 yuan per knife holder, and the blade makes a profit.

So the equation is x=400.

That is, 400 knife holders and 20,000 blades were sold.

The profit of factory A is 8400* (yuan.

Then the profit of factory B is 2 * 4200 = 8400 yuan.

If the number of knife holders sold by B is x, then the number of blades is 50x, according to the title, 50x*(

x=400 So factory B sold 400 knife holders and 20,000 blades.

1. Fill in the blanks.

8. d+c-b-a

Second, it refers to the vertical selection of the title hand amusement.

1, C) 3, B 4, C 5, A 6, A 7, C 8, D

1)0--10 0+10 10 (2)-23 -13 (3)120 (4)0 (5)4 -1 (6)-10 -6 0 (7)1 1 1 (8)-a-b+c+d (9)>

Multiple choice questions Okay, I won't be able to do it later, and I won't be excited.

I said dude, so much, it's very ——— I guess only idle people will do it for you.

Even if you make it, it won't give you a point.

1 The solution of the equation 5-a(1-x)=8x-x(3-a) about x is negative, so what is the range of values for a?

5-a(1-x)=8x-x(3-a)

5-a+x=8x-3x+3a

4x=4a-5

x=5/4-a

Because the solution is negative, so x 0, so 5 4-a 0, so a 5 4

2 If|2x+1|=-2x-1,|3x+5|=5+3x, then what is the range of x values?

Because |2x+1|=-2x-1, so 2x+1 0, the solution is x -1 2

Because |3x+5|=5+3x, so 3x+5 0, the solution is x -5 3

In summary: -5 3 x -1 2

3 Given that x+2y=4k 2x+y=2k+1 and 0 y-x 1 then what is the range of k values?

Get: y-x=2k-1

Because 0 y-x 1, 0 2k-1 1

Solution 1 2 k 1

4 How many negative integer solutions are known about the group of inequalities for a, x-a, 0, x-2, 0?

Because x-2 0, so x2, because x-a 0, so x a

Please check the completeness of this question.

5 Given 2(a-3) 2-a 3, what is the set of solutions for inequality a(x-5) 4(x-a)?

Because 2(a-3) 2-a 3, the solution is a 24 7

The inequality a(x-5) 4(x-a) can be reduced to (a-4)x a

Because a 24 7, a-4 0, the inequality is x(a)(a)(a-4).

-a(1-x)=8x-x(3-a)

5-a+ax=8x-3x+ax

5-a=5x

x=1-a\5

Because the x solution is negative, 1-a 5<0

So 152, |2x+1|=-2-1,|3x+5|=5+3x2x+1|It can't be negative, maybe it's wrong.

3、x+2y=4k①2x+y=2k+1

1 formula minus 2 formula, x+2y-(2x+y)=4k-(2k+1)y-x=2k-1

Because 0 y-x 1, 0 2k-1 1, and finally 1 2 = 0, i.e., a<=x, x<2, so there are infinite negative integer solutions for the inequality group of a x-a 0 x-2 0.

a-3）＜2-a/3

2a-6< 2-a 3, 2a+a 3<8, a<24 7 in a(x-5) 4(x-a).

ax-5a>4x-4a,ax-4x>-4a+5a,x(a-4)>a,x>a\(a-4)

Because a<24 7, substitute x>(24 7) (24 7-4), and finally get x>-4

1. The value of the algebraic formula (2ax -x +3x+2)-(5x -3x-6bx) is independent of x, that is, the coefficient related to x is zero. That is, 2a-5-1 = 0, 6 + 6b = 0

So a=3, b=-1;

2ab-3[a+2（-a+2b）-3(ab-b)]=2ab-3[a-2a+4b-3ab+3b]=11ab+3a-21b=-3

2、∠a+∠b=90°，∠a/∠b=2:3,∠a=36°,∠b=54°；180°-∠a-（180°-∠b）=18°

3. Let the speed of the two cars be x,y; Then, 4x+6y=510, the solution is x=45, y=55

4. Point E**?

Lost. The cost of a washing machine is 990 (1+10%) = 900 yuan.

The other is 990 (1-10%)=1100 yuan.

The sum of costs is 1100 + 900 = 2000 yuan.

And the actual harvest is 990 2 = 1980 yuan.

So I lost 20 yuan.

6 times 2 tenths, and then multiplied, that is, Xiao Ming was defrauded of yuan.

There's no interest tax, right?

Solution: Set one year x yuan, three years (10000-x) yuan.

x*(solution to x=4000, then:

10000-x=6000

Answer: 4,000 yuan for one-year term and 6,000 yuan for three-year term.

Let one year be x and three years be y

List the returning pigs; x+y=10000 （1）

2) Convert (1) to x=10000-y, bring in (2), and multiply it yourself.

The one-year deposit and three-year deposit are $x and $ y respectively. then there is x+y=10000

Solving the system of equations yields x=4000

y=6000

1. Solution: If the answer is correct, the wrong answer is (50-x).

According to the title:

3x-(50-x)=142

3x-50+x=142

4x=192x=48

Answer: In the seventh grade, I got 48 questions right, and I answered 2 incorrectly or did not answer 2 questions.

2. Grade 7 (2) class? Yes, because the full score is 150 points, if you want to get 145 points, you only need to answer 5 questions without answering or answering incorrectly.

2. 1. Solution: Set the specified time to be x minutes.

15*(x-24)=12*(x+15) [using the equation of distance equality] 15x-360=12x+180

3x=540

x=180 tested: x=180 is the solution of the original equation.

A: The allotted time is 180 minutes.

2. Solution: According to the meaning of the question:

Original = 156*15

2340 km.

A: The distance between his house and the railway station is 2,340 kilometers.

1) Denominator: 7(1-2x)=3(3x+1)-3, parentheses: 7-14x=9x+3-3

Move Items Merge items of the same kind 5x=7

The coefficient is reduced to one x=7 5

2) x 2-3 2+2-x 3=2 3 (1+1 4+x 2) deparentheses x 2-3 2+2-x 3=2 3+1 6+1 3x shift x 2-x 3-1 3x=3 2-2+2 3+1 6Merge homogeneous terms -1 6x=1 3

x=12x-x/3+2/3+1=0

35/3x=-5/3

x=-1/7

3x-1)/4+(2x+1)/3

1/4x-1/4+1/3x+1/3

7/12x+1/12

Substituting x=-1 7 yields.

Original = 7 12 * (-1 7) + 1 12

Don't be too lazy.

1 solution yields 67 = 23x, x = 67 23

2 solution, x=8 3

3 first touches x=-1 7, and the original is equal to -10 7 4+5 7 3=-30 7+20 7=-10 7

Multiply 21 by both sides, multiply 12 by the second two, and the second x is 1/7 of the minus.