If the length of a rectangle increases by 3cm, its area will increase by 15cm. If the width decreases by 1cm, its area will decrease by 7cm. Find the area of the original rectangle

If the length of a rectangle increases by 3cm, its area will increase by 15cm. If the width decreases by 1cm, its area will decrease by 7cm. Find the area of the original rectangle

If the length of a rectangle is increased by 3cm, the area will be increased by 15cm
So the width is 15 △ 3 = 5cm
If the width is reduced by one centimeter, the area will be reduced by seven square centimeters
So the length is 7 △ 1 = 7cm
The area is 5 × 7 = 35cm and 178;

When the image of the first-order function y = (k-1) x + (- K-5) passes through two, three and four quadrants, the range of K value is calculated?

∵ the image of the linear function y = (k-1) x + (- K-5) passes through two, three and four quadrants
∴K-1

Finding the partial derivative AZ of the function z = ln (x + Y2)/ ax.az/ay And total differential

ez/ex
=1/(x+y^2) *1
=1/(x+y^2)
ez/ey=1/(x+y^2)* (2y)
=2y/(x+y^2)
dz=ez/ex dx+ ez/ey dy
=1/(x+y^2) dx+ 2y/(x+y^2) dy

A. B, C, D, e five people in a full score of 100 points in the examination, a score of 94, B is the first, C score is the average score of a and D, D score is the average score of five people, e more than C 2 points, is the second, then B got how many points?

According to (1) analysis, C is the average score of a and D, and if d > A, there is a < C < D; according to (2) analysis, D score is even, which is 96 or 98. When d = 98, it does not conform, and is rounded off; when d = 96, C = (94 + 96) △ 2 = 95, e = 95 + 2 = 97, 5 × 96 - (94 + 95 + 96 + 97), = 480-382, = 98; a: B gets 98

Translation law of inverse scale function

First order function: y = KX + B move left and right: y = K (x + n) + B, "left plus right minus" move a few units, add (subtract) a few units up and down: y = KX + (B + n) "up plus down minus" inverse scale function: left and right translation changes the position of y = (1 / x + m) + n m at denominator, which is also "left plus right minus" move up and down

Solve the following equation (1) 19 / 11x + 7 / 11 + x = 3 / 11x-4
（2） 3x-2=1/2x+1
(3) -3/4x+3=4x-6
(4) 2/3x-5=3/2x+3
(5) 5x-3.5=-2.5+4.5
(6) 5a+8-6a=2a+3

（1） 19/11x+7/11+x=3/11x-4
16/11x=-4-7/11
16/11x=-51/11
x=51/16
（2） 3x-2=1/2x+1
2.5x=3
x=1.2
(3) -3/4x+3=4x-6
13/4x=-9
x=-36/13
(4) 2/3x-5=3/2x+3
3/2x-2/3x=-8
5/6x=-8
x=-9.6
(5) 5x-3.5=-2.5+4.5
5x=5.5
x=1.1
(6) 5a+8-6a=2a+3
8-a=2a+3
3a=5
a=5/3

Factorization a2b2-a2-b2 + 1=

a2b2-a2-b2+1 =a2(b2-1)-(b2-1) =(a2-1)(b2-1) =(a+1)(a-1)(b+1)(b-1)

As shown in the figure, in △ ABC, points D and E are on BC, and ∠ 1 = ∠ B, ∠ 2 = ∠ C, BC = 10cm, then the perimeter of △ ade=______ ．

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How many square meters is l Zhang, and how many square meters is 1 Zhang

If 1m = 3 feet and 1m = 10 feet, then 1m = 0.3 feet and 1m = 0.3 * 0.3 = 0.09 square feet

The basketball court is 28 meters long and 15 meters wide. Draw a plan with a scale of 1:1000. Thank you

Length 28 △ 1000 × 100 = 2.8 cm
Width 15 △ 1000 × 100 = 1.5cm
Just draw a rectangle to this size