Solve a math problem in junior high school Please!

4200 + 140x-60x-2x 2-500 = 1950 after finishing, x 2-40x-875 = 0

x-20)^2-400-875=0

x-20)^2=1275

x=20+5*51 under the root, or x=20-5*51 under the root

4200-60x+140x-2x*x-500-1950=0x*x-40x-875=0

There is no integer solution.

is an irrational number. 20 plus or minus 5 root number 51

x1=x2=This is a quadratic one!

I'll count, but I won't tell you--- I'm afraid your teacher will blame me.

Hahaha love haha.

I won't forget about this, so I'll analyze it for you.

Question 1: The parabola passes through the points (0,0) and (170,0) points, and substituting the analytic formula respectively to find b and c. So there is analytical.

Question 2: This maximum distance is the distance of the parabolic vertex from the x-axis, and the vertex coordinates formula of y=ax +bx+c(a≠0) is.

b 2a, (4ac-b) 4a), which can be found directly by the analytic formula of the first question.

The third question, the first one: a=90°, oab=30°, so oap=60°. Therefore, the slope of the straight line AP is there, and it can be found directly after point A.

The second type: b=90°, directly substitute x=170-80=90 into the simplified formula, and the p coordinates that can be found.

The third type: p=90°, ab is a right-angled edge, over the diameter ab to make a circle, the intersection of the circle and the parabola is the point p, you will find that the point p coincides with a. So this exclusion.

The ** of the mirror and the bezel is 195-45 = 150 yuan.

If the width of the mirror is x meters, its length is 2x

Mirror** is 2x*x*120 yuan.

The border ** is 2*(2x+x)*30 yuan.

The equation 2x*x*120+2*(2x+x)*30=150 is solved to get x=1 2 or -5 4

This value must be positive, and the length of the mirror is 1 meter, 1 2 meters.

Hope mine helps you!

Solution: Length: 2xCircumference: 6x

So there are 120 2x 2+6x 30+45=yy=240x 2+180x+45

y=195.

240x＾2+180x-150=0

Solution: (2x-1)(4x+5)=0

x=1 2 negative rounding.

Length 1mWidth 1 2m

1) Calculate ad==2 2, and e is the midpoint of ad, so de=ae=2

So be=6, ec=3

Because ab de=ae cd=be ce= 2, cde is similar to eab

2) Because ec bc = dc ec = de be= 3 3. CDE is similar to CEB.

(1) It can be calculated that ad=2 2

de=ae=√2

be=√6，ec=√3

ab/de=ae/cd=be/ce=√2

So similar. 2）be=√6，ec=√3，bc=3

So ceb=90°

bc/ce=be/de=ce/cd=√3

So it's similar.

Dadizhiling, hello:

Solution: (1) Set the purchase price of M-shaped clothing to be X yuan.

The price of the sale is 75 yuan, and the sales can still make a profit of 50% according to the 20% discount, then the equation can be listed as:

X 40 means that the purchase price of M-shaped clothing is 40 yuan.

2) The price is 75 yuan at the time of sale, and the price of each piece is reduced by 20% on the basis of 20% off.

The actual selling price of the M-shaped clothing to carry out the ** activity is 75

The profit from sales is 60 x 40 20 x.

And the functional relationship between the number of sales per day y (pieces) and the price reduction x (yuan) is y 20 4x The profit obtained from the daily sale of m-shaped clothing during the ** period:

w＝（20－x）（20＋4x）

4x^2＋60x＋400

4（x－15/2）^2＋625．

When x 15 2 yuan), the maximum profit w is 625 yuan.

(1) The price of the sale is 75 yuan, and the profit can be made by selling at 20% off (75 * 80% - purchase price) = purchase price * 50%.

Solution purchase price = 40 yuan.

2) w = quantity sold per day y (pieces) * how much money earned per piece = y * 40 * 50% -x).

20+4x) *20-x)

4x^2+60x+400

4(x^2-15x-100)

4[(x-15/2)^2 -225/4 -100]=-4(x-15/2)^2+625

When x=15 2=yuan, w is up to 625 yuan.

9 teams. If there are x teams, then there is 3x+2(x-6)=33, and the solution is x=9

Set to pass x people.

3x+3x·x+3x=864×50%

x=12 passed 3x people in the first round 3x people in the second round and wore x people on average in the second round The neighborhood committee also passed in the second round So the second round passed a total of 3x·x+3x people.

Let the taproot of this plant grow a branch.

1+a+axa/3+2axa/6=109a=12

Analysis: This problem can be set up that an average of one computer in each round of infection will infect x computers, then a total of (1+x) will be infected after the first round, and a total of (1+x)+x(1+x) that is, (1+x) 2 will be infected after the second round, and the value of x can be found by using the equation, and a total of (1+x)3 will be infected after 3 rounds, and the number can be judged by comparing the size of the number with 700

Answer: Solution: If each computer in each round of infection will infect x computers on average, according to the problem: 1+x+(1+x)x=81, and (1+x)2=81, then x+1=9 or x+1=-9, x1=8, x2=-10 (rounded), (1+x)3=(1+8)3=729 700

A: In each round of infection, an average of 8 computers will be infected per computer, and after 3 rounds of infection, more than 700 computers will be infected.

1) If the number of infections per person a day is x, Xiao Ming alone at the beginning; The number of newly infected people on the first day was x, and the number of co-infected people as of the first day was x+1;The number of newly infected people on the second day is (x+1)*x, and the number of co-infected people is (x+1)*x+x+1=225 on the second day, so x=14, then the first communicator has a total of 28 people in two days. (2) The number of newly infected people on the third day is 225*(14-5)=2025, the number of co-infected people as of the third day is 2025+225=2250, the number of newly infected people on the fourth day is 2250*(14-5-5)=9000, and the number of co-infected people as of the fourth day is 9000+2250=11250. The above is a detailed analysis.

If you are familiar with the number series, you can simplify the formula.

If the width of the lace is x meters, then (1+x)*(1+x)-1*1=44%*1 can be obtained from the title

1+x)*(1+x)=

The solution is x=

This problem should be done in the same area method.

Let the width of the lace be x, and the area of the lace is 1 times x, because the area is long by wide, and the length is the same as the square cloth, so it is 1

x=44%x=

So the width is meters.

Belch. The calculation seems to be too. Or did I miscalculate? Submit it and talk about it.

The first two were wrong.

Let the lace width be x.

The resulting side length is 1+2x. (The one on the first floor, that's what went wrong here, shouldn't be 1+x.) On the second floor, it should be widened on all sides, so the length is not equal to the length of the side of the square).

After lace area: (1+2x) 2

Cloth area: 1

Lace area: From this we get the equation: (1+2x) 2=1+

The solution is x=

Solution: Set the width of the lace to x

Because the lace area is 44% of the square fabric area

From the meaning of the title (1+x) 2=x=