Synchronous practice and evaluation 2.7 accurate and approximate numbers

Synchronous practice and evaluation 2.7 accurate and approximate numbers

Scientific counting method: for example, 520000 scientific counting method is 5.2 times 10 to the 5th power, that is to say, the highest order of the original number is regarded as you write the following numbers after the decimal point, round off the zero at the end, and then look at how many digits the original number is, and subtract one of its digits. For example, 520000 is 6 digits, which is multiplied by 10 to the 5th power

Target and detection. 15, 16, 17 pages of the answer ah

In Figure 1, an equilateral triangle pattern is made up of several small circles. There is a circle on the top layer, and each layer below has one more circle than the previous layer, with a total of N layers stacked. Invert Figure 1 and the original figure 1 to form the shape of Figure 2. In this way, we can calculate the number of circles in Figure 1 as 1 + 2 + 3 = +n= . ...

Synchronous practice and evaluation of mathematics in the first year of junior high school

This kind is not usually found
Give you an answer that is not the answer:
It's beyond the mountain

X / 3 = Y / 3, 10% X-7% y = 1%

It can be seen from the form that x = y, so substituting into the two forms, 3% x = 1%, so x = 1 / 3, so y = 1 / 3

The solution of 2x-y = 1 3x + 2Y = 2 is the solution of the quadratic equation 5x-my = - 11

According to the meaning of the title:
2x-y=1 ①
3x+2y=2 ②
① * 2 is 4x-2y = 2 ③
Then ③ + ② has: 7x = 4 → x = 4 / 7, substituting x = 4 / 7 into formula ①, y = 1 / 7
Substitute the above x = 4 / 7, y = 1 / 7 into the quadratic equation 5x my = - 11
The solution is: M = 97

Simplify 3 (m square of X + m square of Y) - 2 (m square of Y - m square of 1 / 2 x) - (m square of 5x - m square of 7Y)
Thank you

3（x^m+y^m)-2(y^m-1/2x^m)-(5x^m-7y^m)
=3x^m+3y^m-2y^m+x^m-5x^m+7y^m
=-x^m+8y^m

Calculation (e.g. - 3 / 2 is negative 3 / 2, not negative 3 divided by 2, if it is a separate '/' is division sign, e.g. (1-3) / 2 is (1-3) divided by 2)
Calculation: - 3 / 2 * {[(1-3) / (- 2 / 3) & # 178;} + 1] * 1 / 7 * (- 1 / 4) & # 178; * (- 3) & # 178; / (3 / 4) & # 179;}
Please answer quickly~

What's your result? The correct result is 1

4x^4+x^3+2x^2+5x+12=0
Just the results

I'm sorry, the equation you listed is solved by mathematical software, and the result is no solution

Why is the adjoint matrix multiplied by the original matrix equal to the determinant of the original square matrix multiplied by the identity matrix?

Remember the concept and properties of the algebraic covalent of a determinant
The algebraic cofactor AIJ of element AIJ of determinant a
The product of the i-th row (or column) of determinant A and its corresponding algebraic covalent = | a|
The product of the i-th row (or column) of determinant A and the algebraic covalent corresponding to other rows (or columns) = 0
The adjoint matrix A * of matrix A is the transpose matrix of the matrix composed of the algebraic cofactors of each element of A
A new matrix is obtained by multiplying a by a *,
All elements on the main diagonal are | a | and the other elements are 0,
So AA * = |a|e
Similarly, a * a = | a | E
It's hard to understand. Just think it over

5x + 2 = 2x square 3 / 2T ^ 2 + 4t-2 = 0

x=-2/3
T = (- 4 ± 2 * root (7)) / 3