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The counter example is used to show that the proposition "if M > 1, then x ^ 2-2x + M = 0 has real root" is a false proposition
When m = 2, the original equation is X & # 178; - 2x + 2 = 0
(x-1)²=-1
No real root
If M > 1, then "x ^ 2-2x + M = 0 has real root" is a false proposition
If 2x ^ 2 > x, then x > 1 / 2
Give a counterexample to show that it is a false proposition
When x = - 1, then
2x^2=2*(-1)²=2
2>-1
That is, it satisfies 2x ^ 2 > x, but x = - 1 obviously does not satisfy x > 1 / 2
So it's a false proposition
Please give a counter example to illustrate that "if the square of X is greater than 0, then x is a positive number" is a false proposition
(-1)^2=1>0,-1
In order to solve homogeneous and non-homogeneous linear equations in linear algebra, do you want to reduce coefficient moment or augmented matrix to row simplest form or to row simplest form
In order to solve homogeneous and non-homogeneous linear equations in linear algebra, do you want to change coefficient moment or augmented matrix to row simplest form or to row ladder form? What is the difference between the two? For example, in some problems, if you want to solve the following (non) homogeneous linear equations, what are the requirements of basic solution system and special solution?
Is the simplest form you are talking about standard form? If so, when you solve it, you only need to simplify the equations to the row ladder form. The difference between the two is that the standard form is obtained by the row elementary transformation and the column elementary transformation of the matrix, and the row ladder form is only obtained by the row elementary transformation
A, B and C make 940 parts at the same time. It takes 5 minutes for a part to be made by a, B and C, which is higher than that by B
It takes 1 / 4 more time to make a part, and 2 / 5 less time for C to make a part than for A. how many parts have a, B and C made respectively?
Let a use time x B use time = x / (1 + 25%) = (4 / 5) x min C use time = x * (1-2 / 5) = (3 / 5) x min a = 1 / x B = 1 / (4 / 5) x C = 1 / 3 / 5) x A: B: C = 12:15:2012 + 15 + 20 = 47 A = 940 * 12 / 47 = 240 B = 940 * 15 / 47 = 300 C = 940 * 20 / 47 = 400
How to write the equation x + 2 / 7X = 3 / 4
x+2/7x=3/4
（1+ 2/7）x=3/4
9/7 x=3/4
x=（3/4）*（7/9）
=7/12
There are two granaries A and B, and the ratio of grain storage tons is 5:3. If 5 tons of grain are transported from warehouse A to warehouse B, then the two granaries will store the same amount of grain. How many tons of grain was stored in warehouse a?
The ratio of tons of grain stored in warehouse A and warehouse B is 5:3, 5 + 3 = 8, so warehouse a accounts for 58 tons of grain stored in warehouse A and warehouse B. warehouse A is more than warehouse B: 58 − 38 = 28. Total grain: 5 △ 2 = 5 × 8 = 40 tons. Grain stored in warehouse A: 40 × 58 = 25 tons
(3X-40)*2=80-4X
(3X-40)*2=80-4X
Solution: 6x-80 = 80-4x
6X+4X=80+80
10X=160
X=16
Simple calculation (- 3.75) + 2.85 + (- 1 and 1 / 4) + (- 1 / 2) + 3.15 + (- 2.5)
(- 3.75) + 2.85 + (- 1 / 4) + (- 1 / 2) + 3.15 + (- 2.5)
=（2.85+3.15）-（3.75+1.25+0.5+2.5）
=6-8
=-2
It is known that the sum of the first five terms of a positive proportional sequence is 3, and the sum of the first 15 terms is 39, then the sum of the first 10 terms of the sequence is ()
A. 32B. 313C. 12D. 15
Let the sum of the first n terms of the sequence be SN. From the meaning of the title, we can get S5 = 3, S15 = 39. From the properties of the equal ratio sequence, we can get that S5, s10-s5, s15-s10 are still equal ratio sequence, that is, (S10 − 3) 2 = 3 (39-s10). From the solution, we can get S10 = 12, or S10 = - 9
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