(3x*x+3x*x+x*x)*2=120,

(3x*x+3x*x+x*x)*2=120,

7x²*2=120
x²=60/7
x=-2√105/7,x=2√105/7

How to solve the equation 3x-800 = x-120

2x=680
x=340

Put the nine numbers 1,2,3,4,5,6,7,8,9 in brackets to make the equation hold
（）（）（）=2/1×（）（）（）=3/1×（）（）（）

(2) (7) (3) = 1 × (5) (4) (6) = 1 × (8) (1) (9)

(1) If the image of quadratic function y = - X & sup2; - 2 / 5kx + (2 + 2K + K & sup2;) passes through the left side of a and B, its resolution is obtained
As shown in the figure, points a (Tana, 0) and B (tanb, 0) are on the positive half axis of X axis, point a is on the left side of point B, and a and B are the two acute angles of RT △ ABC with line segment AB as the hypotenuse and vertex C above X axis

The image of y = - X & sup2; - 2 / 5kx + (2 + 2K + K & sup2;) passes through the left side of a and B. according to Weida's theorem, Tana + tanb = - 2 / 5K tanatanb = - (2 + 2K + K & sup2;) cot C = 1 / Tan (a + b) = (1-tanatanb) / (Tana + tanb) = -- 2.5 (3-2k + K & sup2;) / k k = --- 1 or 3 C = 90 COTC = 0 (t

In integers from 1 to 100, find 10 numbers so that the sum of their reciprocal is equal to 1,

1.
1=1-1/2+1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6+1/6-1/7+1/7-1/8+1/8-1/9+1/9
-1/10+1/10
=(1-1/2)+(1/2-1/3)+(1/3-1/4)+(1/4-1/5)+(1/5-1/6)+(1/6-1/7)
+(1 / 7-1 / 8) + (1 / 8-1 / 9) + (1 / 9-1 / 10) + 1 / 10 each two are divided into a group
=1/2+1/6+1/12+1/20+1/30+1/42+1/56+1/72+1/90+1/10
This is the elimination of column terms in a sequence
2. Equal ratio sequence method
1 = 1 / 2 + 1 / 4 + 1 / 8 + 1 / 16 + 1 / 32 + 1 / 32
1/2=3/6=1/6+2/6=1/6+1/3
1/4=5/20=1/20+4/20=1/20+1/5
1/8=9/72=3/72+6/72=1/24+1/12
1/32=3/96=1/96+2/96=1/96+1/48
Substituting
1=1/6+1/3+1/20+1/5+1/24+1/12+1/16+1/32+1/96+1/48
It is also the unchangeable truth of doing mathematical problems to start from scratch, dismantle items again, reduce the difficulty, and do them again

17 / 18 - (7 / 9-2 / 3) simple calculation

17 / 18 - (7 / 9-2 / 3)
=17/18-7/9+2/3
=17/18-14/18+12/18
=15/18
=5/6;
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A simple method of 5 / 12 times 11 plus 5 / 12
Which one goes with which one first?

5 / 12 x 11 + 5 / 12
=5x11 / 12 + 5x1 / 12
=5x of 12 (11 + 1)
=5 / 12 x 12
=5

It is known that the two roots of the quadratic equation AX & # 178; + BX + C = 0 [A is not equal to 0] about X are 1 and - 1 respectively, then a + B + C =?

Because x = 1 is the root of the equation, it can be obtained by substituting x = 1 into the equation
a+b+c=0

Two minus two fifths is equal to two

Eight fifths

The teacher uses a 24 cm long wire to make a rectangular teaching aid. The ratio of length, width and height is 2, 1 and 3. What is the surface area of the rectangle?

1. Find the sum of length, width and height: 24 △ 4 = 6 (CM)
2. Length: 6 × 1 / 3 = 2 (CM)
3. Width: 6 × 1 / 6 = 1 (CM)
4. Height: 6 × 1 / 2 = 3 (CM)
5. Surface area:
（2×1＋2×3＋1×3）×2=22（cm²）