Did someone help me solve two math problems in my first year of junior high school?

1.Let the waist 2x, the bottom y, according to the problem there are x+2x=9 x+y=15 solution x=3, 2x=6, y=12 (round) because the sum of the two waists = bottom.

or x+2x=15 x+y=9 to get x=5, 2x=10, y=4, i.e., waist 10, bottom 4

2.Counter-evidence.

If it is not on a straight line, then the three points form a triangle, and ab+bc is greater than ac, which contradicts ab+bc=ac, and the drum hypothesis is not true, so the problem is proven.

1.If 3/2 waist = 9 cm, then waist = 6 cm.

1/2 waist + bottom edge = 15 cm.

Bottom edge = 12 cm.

2 waist = bottom edge.

Insufficient to form a triangle.

If 3/2 waist = 15 cm, then waist = 10 cm.

1/2 waist + bottom edge = 9 cm.

Bottom edge = 4 cm.

So waist = 10 cm, bottom edge = 4 cm.

2.Drawing Method: 1Make a line segment AC

2.Pass the point a, point c to make the line segment ab, cb, so that ab + cb = ac to find ab, bc, ac in a straight line.

Theory: If the sum of the two edges equals the third side, then the three line segments are on a straight line.

1.If the waist is 9 3 * 2 = 6, then the three sides are 6, 6, 12, and cannot form a triangle.

So the waist is 15 3 * 2 = 10, and the three sides are 10, 10, 4

The answer to the first question is shown above, and the second question: Assuming that the three points are not on the same straight line, then ab+bc=ac is not always true, so the three points are on the same straight line.

The circumference of the triangle is divided into two parts, 9cm and 15cm, one of which is the waist of the times, and the other part is the waist and bottom of the times, but the waist of the times is not sure whether it is 9cm or 15cm, so the waist is 6cm or 10cm

Because the sum of the two sides of a triangle is greater than the third side, ab+bc=ac cannot be a triangle, so the three points can only be connected end to end in a straight line.

Question 2 (Counter-Evidence).

ab+bc=ac

Let's say they're not in the same straight line.

Then three points in the plane can form a triangle.

It can be seen from the nature of the triangle.

The sum of the two sides of the triangle is greater than the third side.

So the assumption is not valid.

So the three points must be in the same straight line.

Solution: Let x-2=t then x=t+2

Then the original formula = 4(t+2) 4 + 2(t+2) 3 + t+2)-3=4(t 2+4t+4) 2 + 2(t+2)(t 2+4t+4) +t-1 (, merge similar terms).

4(t^4+8t^3+24t^2+32t+16)+2(t^3+6t^2+12t+8) +t-1

4T 4+34T 3+108T 2+153T+79 T = x-2, 4(x-2) 4+34(x-2) 3+108(x-2) 2+153(x-2)+79

1. Let the distance be s, then 1 3s+, and solve s=30 kilometers.

2. From A to B is the downstream flow, the speed = hydrostatic velocity + the water velocity = 8 + 2 = 10, from B to C is the countercurrent, the speed is the hydrostatic velocity - the water velocity = 8-2 = 6, the distance, AC + CB = AB, let the downstream time be t, the countercurrent time is (3-t), then 2 + 6 (3-t) = 10t, t = 5 4 hours, ab = 10t = kilometers.

1.Half an hour after driving to the station, so the distance after 2 3 is 20km, and 20 divided by 1 3 equals 30km

2.Let the distance from A to B be X

The downstream velocity is 8+2=10, and the countercurrent velocity is 8-2=6x-2) 10=3-(2 6)x=

1.If "*" is specified as an operator symbol, and a*b = a to the power of b - a power of b, 4*(2*4) is calculated

The problem of prescribing the notation should be there in elementary school.

The key to this question is to distinguish what number a b represents in the following equation.

a*b = a to the power b - b to the power of b.

So first calculate (2*4) = a to the power b - b to the power a = 2 to the 4th power - 4 to the power of 4 = 0

4*(2*4) is converted to 4*0 = a to the power b - b to the power a = 4 to the power of 0 - 0 to the power of 0 to the power of 0 = 1-0 = 1

Question 2 =2]?? How can there be =?? Typing wrong, in fact, this kind of question, pay attention to the order of operation, pay attention to the positive and negative signs, and generally will not make mistakes.

Question 1: 2*4 = 2 4-4 2 = 0

The answer is 1, and you made a mistake in question 2, right? What is the equal sign in the middle of the equation?

If you are struggling to study, you should cultivate more self-thinking, do more hands-on problems, and take your time. :)

1. It is known that it satisfies 2/3 of the square + 5 m = 0 to get the initial x=5 m = 0 As for y, it has never appeared from beginning to end.

So (2x squared - 3xy + 6y squared) - m (3x squared - xy + 9y squared) = 50-15y + 6y 2

2. Because xy x+y = 3, so xy = 3 (x + y) (1).

Substitute equation (1) into the evaluation equation:

2x-3xy+2y/-x+3xy-y

2x-9x-9y+2y/-x+9x+9y-y=-7x-7y/8x+8y

The figure is not clear. All you need to do is find the inner wrong angle and the equal line segment and the like.