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Judgment: if two decimals are multiplied, the number of decimal places of the product is equal to the sum of the number of decimal places of two factors
wrong
For example, 1.2 × 1.5 = 1.8
If √ (2x + 7) = 3, (4x + 3Y) & # 179; = - 8, find & # 179; √ (x + y)
√(2x+7)=3,(4x+3y)³=-8,
2x+7 = 9
2x = 2
x =1
4x+3y = -2
3y = -2 -4 = -6
y = -2
Find & # 179; √ (x + y)
= ³√ ( 1-2)
= ³√ (-1)
= -1
Q: how to do the cubic equation 3x-y + Z = 3 2x + y-3z = 11 x + y + Z = 12
Work out the formula
3x-y+z=3 (1)
2x+y-3z=11 (2)
x+y+z=12 (3)
(1) + (2)
5x-2z=14
z=(5x-14)/2
(2) - (3), got it
x-4z=-1
z=(x+1)/4
(5x-14)/2=(x+1)/4
It's time to tidy up
9x=29
x=29/9
z=(x+1)/4=19/18
X = 29 / 9, z = 19 / 18 substituting (3)
y=12-x-z=12-29/9-19/18=139/18
x=29/9 y=139/18 z=19/18
1.3xy -4xy-(2xy)
Is it 1.3 or the first question
3xy-4xy-（-2xy）
The common factor XY is obtained by the law of association
3xy-4xy-（-2xy）
=（3-4+2）xy
=xy
(2/3xy^2-2x^2y^3+4xy)÷(-2xy)
(2/3xy^2-2x^2y^3+4xy)÷(-2xy)
=(2/3xy^2)÷(-2xy)-(2x^2y^3)÷(-2xy)+(4xy)÷(-2xy)
=-1/3y+xy^2-2
Let X be 1 / 3 and y be - 2 / 3, and find 1-2xy / 3xy-2 + 3xy / 4xy ^ 2
1-2/3-2+3/4*(-3/2)=-67/24
Let a, B, C be an equal ratio sequence, X be the mean of a, B, and y be the mean of B, C, then a / x + C / y=
How to do it
2
Let the common ratio of the equal ratio sequence be Q
x=(a+b)/2
=(a+aq)/2
y=(b+c)/2
=(aq+aq^2)/2
a/x+c/y
=a/[(a+aq)/2]+aq^2/[(aq+aq^2)/2]
=2/(1+q)+2q/(1+q)
=(2q+2)/(q+1)
=2
Let a, B, C be an equal ratio sequence, X be the median of a, B, and y be the median of B, C, then a / x + C / y
Let a, B, C be an equal ratio sequence, X be the median of a, B, and y be the median of B, C, then a / x + C / y
a. So B ^ 2 = AC, x = (a + b) / 2, y = (B + C) / 2A / x + C / y = 2A / (a + b) + 2C / (B + C) = 2A (B + C) + 2C (a + b) / (a + b) (B + C) = 2 (AB + AC + Ca + CB) / (a + b) (B + C) = 2 (AB + B ^ 2 + Ca + CB) / (a + b) (B + C) = 2 (a + b) (b + C) / (a + b)
If a > b, what is the eccentricity e of hyperbola x ^ 2 / a-y ^ 2 / b?
a+b=10,ab=16,a>b
So a = 8, B = 2
So the eccentricity of x ^ 2 / 8-y ^ 2 / 2 = 1 is
(8 + 2) / 8 and then root
The answer is half root five
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