Mathematics book grade 7 Volume 2 p173 to p174

1,B
2, (1) the score of x = 3 is 0, and the score of x = - 3 is meaningless
(2) The value of x = - 2 / 3 is 0, and x = 4 / 5 is meaningless

｛2x-1／5 + 3n-1／4 =2,3x+1／3 - 3y+2 ／4 = 4／3

The title should be 2x-1 / 5 + 3y-1 / 4 = 2
4(2x-1)+5(3y-1)=40
8x+15y=49 (1)
3x+1／3 - 3y+2 ／4 = 4／3
4(3x+1) -3(3y+2)=16
12x-9y=18 (2）
(1) * 3 - (2) * 2
24x+45y-24x+18y=49*3-18*2
63y=111
y=111/63
x=237/84

Monotone increasing interval of function f (x) = 1 / 3x ^ 3-1 / 2x ^ 2-2x + 5

First, find out the derivative function as: x ^ 2-x-2, let x ^ 2-x-2 > 0 get x > 2 or X

Finding the monotone interval of F (x) = 1 / (xlnx) (x > 0 and X ≠ 1)

Do it by derivation
f'(x)=-(xlnx)'/(xlnx)^2
(xlnx)'=lnx+1
x> When 1 / E, the derivative is negative,
(0,1 / E) increase

Seek the calculation method of two mathematical problems. To detailed process!
1. A bank deposit is fixed for five years, with an annual interest rate of 2.88%. After maturity, the income interest must pay the individual income tax at the rate of 20%. In this way, after deducting the individual income tax at maturity, the actual interest can be 576 yuan. Q: how much is the actual capital and interest?
2. When does the hour hand and the minute hand on the clock face perpendicular to each other between 6 o'clock and 7 o'clock? (the result is expressed with a fraction). If the minute hand is 11 cm long, what is the distance from 6 o'clock to the moment when the minute hand is perpendicular to each other? (the result retains π)

The first question is set as X Yuan x 2.88% * 5 * (1-20%) = 576x 0.144 * 0.8 = 576x = 4000 / 0.8x = 50005000 + 576 = 5576 (yuan). When the second question is six o'clock, the two angles should be 180 degrees and perpendicular to each other, that is, the minute hand should catch up with 90 or 270 degrees per minute, the minute hand should walk 6 degrees, the speed of the hour hand is one twelfth of the minute hand, 0 per minute

In the acute angle △ ABC, ad bisects ∠ BAC, CD ⊥ ad, the perpendicular foot is D, and the point E is the midpoint of BC, connecting De

Extend CD to f so that CD = DF
Even BF
Knowing that a, B and F are collinear from "three lines in one"
De is the median line of triangle CBF
It is de | BF
Get proof

Given the square of a + AB = 3, the square of AB + B = 1, try to find the square of a + 2Ab + B and the square of a-b

It can be seen from the question: the square of a + 2Ab + B = the square of a + AB-Ab + B = 3-1 = 2
Square of a - square of B = 3 + 1 = 4

Y = 53x ^ 2, dy / DX, please

dy/dx=106x

Make it clear what each step counts
In the three grades of junior middle school in a middle school, the number of students in grade one is nine tenths of that in grade two, and the number of students in grade two is four fifths of that in grade three?
Who will? When answering, we must make the process clear, not just tell the number
The number of students in grade two is five times that of grade three, not four times that of grade three. I just made a mistake. Sorry

Regarding the number of junior three students as unit "1"
The number of students in grade two is 1 * 5 / 4 = 5 / 4
The number of students in grade one is 5 / 4 * 9 / 10 = 9 / 8
Middle school junior middle school three grades 1 + 5 / 4 + 9 / 8 = 27 / 8
The number of junior high school students accounts for 1 / 27 / 8 of junior high school students = 8 / 27

(1) the quadratic function y = x2-4x + 3 is changed into the form of y = (X-H) 2 + K by the collocation method;
(1) the quadratic function y = x2-4x + 3 is changed into the form of y = (X-H) 2 + K by the collocation method;

y=x²-4x+3
=x²-4x+4-4+3
=(x²-4x+4)+(-4+3)
=(x-2)²-1

Mathematics book grade 7 Volume 2 p173 to p174