A calculation problem (using the square difference formula) (1) The correct result is () A.(x-2)(2+x)=x^2-2 B.(3x-2)(x+2)=3x^2-4 C.(7x-y)(7x+y)=49x^2-y^2 D.(x^2-y^2)(x^2-y^2)=x^4-y^4 (x ^ 2 means the square of X, y ^ 2 means the square of Y, x ^ 4 means the fourth power of X, and Y ^ 4 means the fourth power of Y.) (2) (0.5x-1 / 2) (1 / 2x + 0.5) = (to write the calculation process) (1 / 2 means 1 / 2) After I check with the teacher, I'll see if you are right! I am the third level answer (only {he} her second question has a process)

A calculation problem (using the square difference formula) (1) The correct result is () A.(x-2)(2+x)=x^2-2 B.(3x-2)(x+2)=3x^2-4 C.(7x-y)(7x+y)=49x^2-y^2 D.(x^2-y^2)(x^2-y^2)=x^4-y^4 (x ^ 2 means the square of X, y ^ 2 means the square of Y, x ^ 4 means the fourth power of X, and Y ^ 4 means the fourth power of Y.) (2) (0.5x-1 / 2) (1 / 2x + 0.5) = (to write the calculation process) (1 / 2 means 1 / 2) After I check with the teacher, I'll see if you are right! I am the third level answer (only {he} her second question has a process)

(1) Choose C
（2）=（0.5x)"2-0.5"2
=0.25x"2-0.25

Mathematics of the second grade of junior high school Volume I calculation of the square difference formula
(a + 2b) (a-2b) - half B (a-8b) 2009 squared - 2008x2010

(a + 2b) (a-2b) - half B (a-8b) = a ^ 2-4b ^ 2 - [b (a-8b) / 2] = a ^ 2-4b ^ 2 - (AB / 2) + 4B ^ 2 = a ^ 2-AB / 2
Square of 2009 - 2008x2010 = 2009 ^ 2 - (2009-1) (2009 + 1) = 2009 ^ 2-2009 ^ 2 + 1 ^ 2 = 1

A computer dealer plans to purchase a batch of computer cases and LCD monitors. If 10 computer cases and 8 LCD monitors are purchased, a total of 7000 yuan will be needed; if 2 computer cases and 5 LCD monitors are purchased, a total of 4120 yuan will be needed. (1) what are the purchase prices of each computer case and LCD monitor? (2) According to the market situation, the profit from selling a computer case and a LCD is 10 yuan and 160 yuan respectively. The dealer hopes to make a profit of no less than 4100 yuan after selling these two kinds of goods. What kinds of purchase plans does the dealer have? Which scheme is the most profitable? What is the maximum profit?

(1) Suppose the purchase price of each computer case and LCD is x, y yuan respectively. According to the meaning of the question, we get: 10x + 8y = 70002x + 5Y = 4120. The solution is: x = 60y = 800. Answer: the purchase price of each computer case and LCD is 60 yuan, 800 yuan respectively. (2) suppose the dealer buys m computer cases and 50-m LCD. According to the meaning of the question, we get: 60m + 800 (50 − m) ≤ 2224010m+ 160 (50 − m) ≥ 4100, the solution is: 24 ≤ m ≤ 26, because m needs to be an integer, so m can take 24, 25, 26, so there are three ways to purchase: ① computer box: 24, LCD: 26, ② computer box: 25, LCD: 25; ③ computer box: 26, LCD: 24. Scheme 1's profit: 24 × 10 + 26 × 160 = 4400 (yuan), scheme 2's profit: 24 × 10 + 26 × 160 = 4400 (yuan) Profit: 25 × 10 + 25 × 160 = 4250 yuan, profit of scheme 3: 26 × 10 + 24 × 160 = 4100 yuan, profit of scheme 1 is 4400 yuan

1 minus the reciprocal of 1-x equals 1 minus the reciprocal of x equals 1
How does the second part count

1－1／﹙1－x﹚＝1－1／x
1／﹙1－x﹚＝1／x
1－x=x
x=½
It is proved that x = - 189; is the solution

Given that the solutions X and y of the system of equations 2x + 3Y = k3x − 4Y = K + 11 satisfy the equation 5x-y = 3, the value of K is obtained

The solution of the equations about X is: x = 7K + 3317y = k − 1117, substituting 5x-y = 3 to get: 5 × 7K + 3317-k − 1117 = 3, the solution is: k = - 12534

Finding a zero point of function y = 3x ^ 3-2x ^ 2 + 3x-6 by dichotomy

Finding a zero point of function y = 3x ^ 3-2x ^ 2 + 3x-6
y'=9x^2-4x+3
Let y '= 0,
9x^2-4x+3=0
Then I'll solve it myself

It is known that the abscissa of the intersection of the parabola y = ax ^ 2 + BX + C and the X axis is - 1, A-B + C=

Substituting x = 1 into the original formula
We obtain y = A-B + C
Y = 0 because it intersects the X axis
a-b+c=0

Known plane rectangular coordinate system X, O, Y. parabola y = - x square + BX + C passing through point a, a (4,0) B (1,3)
Given the plane rectangular coordinate system X, O, Y. the parabola y = - x square + BX + C passes through point a, a (4,0) B (1,3 ask (1) to find the function expression of the parabola and write out the symmetry axis and vertex coordinates of the parabola! Question (2) record the symmetry axis of the parabola as line 1, let the point P (m, n) on the parabola be in the fourth quadrant, the symmetry point of point P about line 1 is e, and the symmetry point of point e about y axis is f, If the area of quadrilateral oapf is 20, then request the value of M, n! Note that there is no picture in this topic, hope talent to solve it!

(1) The equation y = - xsquare + BX + C is replaced by a (4,0) & nbsp; B (1,3 & nbsp;) to obtain B and C. that is, 0 = - 16 + 4B + C and 3 = - 1 + B + C & nbsp; are combined to obtain B = 4 and C = 0

{x + y + Z = 7, x + 2Y = 4, z = 3x-2y

z=3x-2y
Substituting x + y + Z = 7
x+y+3x-2y=7
4x-y=7 (1)
x+2y=4 (2)
(1)×2+(2)
8x+x=14+4
9x=18
therefore
x=2
y=4x-7=1
z=3x-2y=4

What is the value of x ^ 2-xy = - 3, 2xy-y ^ 2 = - 8, x ^ 2 + xy-y ^ 2
X ^ 2-xy = - 3, 2xy-y ^ 2 = - 8, find the value of x ^ 2 + xy-y ^ 2 and 2x ^ 2 + 4xy-3y ^ 2

x^2-xy=-3（a）
2xy-y^2=-8（b）
(a) Formula + (b) gives x ^ 2 + xy-y ^ 2 = - 11 (c)
(a) Formula + 2 * (b) formula + (c) = 2x ^ 2 + 4xy-3y ^ 2 = - 30