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           ☆1 equations

[ 1/1 Equation]
    Work: Find the solution of equation -85 = 5n+n（n-1）÷2×-3 .
    Question type: Equation
    Solution:Original question:

-

85

=

5

n

+

n

(

n

−

1

)

÷

2

−

3

    Remove the bracket on the right of the equation:

Right side of the equation =

5

n

+

n

n

×

1 2

−

n

×

1

×

1 2

−

3

=

5

n

+

n

n

×

1 2

−

n

×

1 2

−

3

=

9 2

n

+

n

n

×

1 2

−

3

    The equation is transformed into :

-

85

=

9 2

n

+

n

n

×

1 2

−

3

    After the equation is converted into a general formula, it is converted into:
    ( 3n + 17 )( n - 10 )=0
    From
        3n + 17 = 0
        n - 10 = 0
    it is concluded that:：

n1=

-

17 3

n2=10

    
    There are 2 solution(s).

解一元二次方程的详细方法请参阅：《一元二次方程的解法》

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