Binary choice one question at a time, speed!

Because we want to get 700 grams of 6% saline, that is, salt = 6% · 700 = 42 grams, water = 700-42 = 658 grams.

Now we already have salt = 5% ·200 = 10 grams, water 200-10 = 190 grams.

So we also need 32 grams of salt and 468 grams of water.

So the first should be 400 grams of 8% salt water, and the second one is water = 468-400·92% = 100 grams.

The answer is that B does this type of way is to think about the problem not to be too rigid, not to set up some binary equation as soon as you get the problem, how can you do this? It is to constantly think about new ways to solve problems in the usual practice, and even if you get the result, you have to find a simpler solution.

Finally, let's help you make a binary equation, and give points next time you remember to come up with the problem:

Solution: Suppose we need 8% salt water x grams, water y grams, get:

200*5%+x*8%=6%*700

200*（1-5%）+y=700*（1-6%）

Let the grams of salt water and water with 8% salt content be x and y respectively

700=200+x+y

x=400,y=100

x^2-2/(m-1)x+3/(m-1)=0x1*x2=3/(m-1)

When m-1 0, i.e., m1, x1*x2 0, i.e., there is a positive root and a negative root x1+x2=2 (m-1) 0

So the absolute value of the negative root is large.

(m-1)x-2x+3=0 has a positive and negative root, x1x2=3 (m-1)<0

m<1m-1<0

x1+x2=2/(m-1)<0

So the absolute value of the negative root is large.

Let y=(m-1)x·x-2x+3, the two roots of the equation are the two intersections of the function and the x-axis.

When x=0, y=3, that is, the function intersects the y-axis at the point (0,3), if you want to make the equation have two different signs, then m-1<0,m<1, the symmetry axis of the function is x=1 (m-1)<0, you can draw a rough picture of the function from the above information, and it is obvious that the absolute value of the negative root is large.

If you want to write a process, you can solve it according to the sum of the two roots (less than 0).

1, first of all, there are two roots of this equation, so the equation is written in the form of ax*x+b*x+c=0, and then b*b-4ac>0, the formula applied to this equation should be (-2)*(2)-4*(m-1)*3>0 to solve m<4 3

2, and because the equation has a positive root and a negative root, the product of the two roots (c a) < 0, that is, 3 (m-1)<0 is solved to obtain m<1

In summary, m<1

To see which of the two is the absolute value of the two, it depends on whether the sum of the two is positive or negative, and the sum of the two is (m-1) 2

Because m<1, (m-1) 2<0So the absolute value of the negative root is greater than the absolute value of the positive root.

3(x-1)(x-m)-(7-m 2)x=03x 2-3(m+1)x-3m-(7-m 2)x=03x 2-(3m+3+7-m 2)x-3m=03x 2+(m 2-3m-10)x-3m=0, the two real roots are inverse.

First, there are two real roots, and the discriminant formula is greater than or equal to 0

m^2-3m-10)^2+4*3*3m≥0[(m+2)(m-5)]^2+36m≥0………1) Two are opposite numbers to each other, according to Vedd's theorem.

m^2-3m-10)=0

m^2-3m-10=0

m+2)(m-5)=0

m = -2 or m = 5

m=-2, (1) is not true.

So m=5

Please write clearly, square is very different from x, and besides, the multiplication sign and x look very similar!

m=-2

The calculation is as follows: the equation can be arranged as 3x·x+(m·m-3m-10)x+3m=0 If two real numbers are opposite to each other, then the coefficient of the primary term is 0, i.e., m·m-3m-10=0, (m+2)(m-5)=0

We get m1=-2 , m2=5

where m2=5 is not a real root, which does not fit the meaning of the question, so m=-2

（1）（2）

Round up the first digits yourself.

There is a calculator inside the phone!!

Solution: Let A and B be separated by x kilometers.

x/5-x/7=20

2/35*x=20

x=20*35/2

x=350350 7=50 kmh.

Answer: The original speed is 50 kilometers per hour, and the distance between A and B is 350 kilometers.

20+340)*4=2x

x=360*2

x = 720 A: 720 meters from the valley.

Solution: Let the original velocity x

7x=(x+20) 5 Equations based on invariant distances. The distance is 7x, and the distance is x

x-x÷340×20）÷（340+20）=4-x÷340x=720m

1. Let the original speed of the passenger car be x, then there is 7x=5(x+20) to find x=50 The distance between A and B is 7x, that is, 350km

2. When the horn is blazed, the car is x meters away from the valley, then there is 2x-4*20=340*4 to find x=680 meters (is the meaning of "multiplied") thank you.

1 All solutions: Let the natural growth rate be x

then 800 (1+x) = 1152

x=32+32(1+x)+32(1+x)²=122∴x=

Adopt me, thank you.

Suppose that the average annual growth rate is x

800(1+x)2=1152

1+x)2=

1+x=x=Let's: The average growth rate in February and March is x

32+32(1+x)+32(1+x)(1+x)=12232+32+32x+32(1+2x+x2)=12232x+64x+32x2=26

96x+32x2=26

3x+x2=

x+(x+x+x=

Solution: (1) If Beijing is shipped to Wuhan X, Beijing will be shipped to Chongqing (10-x), Shanghai will be shipped to Wuhan (6-x), and Shanghai will be shipped to Chongqing (x-2).

400x+800 (10-x)+300 (6-x)+500 (x-2)=8000, the solution is x=4,10-x=6,6-x=2,x-2=2

Answer: Beijing shipped 4 units to Wuhan, then Beijing shipped 6 units to Chongqing, Shanghai shipped to Wuhan 2 units, Shanghai shipped to Chongqing 2 units

2) Set up Beijing to Wuhan X station, the freight is:

w=400x+800 (10-x)+300 (6-x)+500 (x-2),-200x+8800, by the title: 2 x 6, so: when x=6, the cost is the lowest, 7600, so: 6 units from Beijing to Wuhan; 4 units were shipped to Chongqing;

4 units are shipped from Shanghai to Chongqing, and the lowest shipping fee is 7600 yuan

Hello, this can't be used with a binary system of equations.

Beijing to Wuhan 4 to Chongqing 6 Shanghai to Wuhan 2; to Chongqing 2

Beijing to Wuhan 6 to Chongqing 4 Shanghai to Wuhan 0; to Chongqing 4 7600 yuan.

Q1: If it is transported from Beijing to Wuhan X, then 400x+800(10-x)+300(6-x)+500(x-2)=8000

x=4q2: Set the freight to be w yuan, from Beijing to Wuhan x sets w=400x+800(10-x)+300(6-x)+500(x-2) 0 x 6

When x=6, w is the smallest, which is 7600

Question 1: Set up Beijing to transport to Chongqing X station, and ship to Wuhan Y station; Then it was shipped to Chongqing (8-x) and Wuhan (6-y).

System of equations: x+y=10 800x+(8-x)500+400y+(6-y)300=8000

The answer is: x=6 y=4

Problem 2: Reducing the shipping cost can make the second equation in question 1 800x+(8-x)500+400y+(6-y)300 less than 8000

i.e. x less than 6 can reduce the overall shipping cost.

The points are in the middle of the class, but she and don't follow her waste vegetable v