The steps are as follows:

(1) Decomposition of quadratic term by cross multiplication (obtaining cross multiplication graph (with two columns).

(2) The constant term f is decomposed into two factors and filled in the third column. It is required that the sum of the cross products of the second and third columns is equal to the original formula, and the sum of the cross products of the first and third columns is equal to dx in the original formula.

x 1=[5-5(？ √35)-? √ 1225]/30?

x2=[ 10+5(？ √35)+? √ 1225)/60+I√3[5(？ √35)-? √ 1225]/60?

x3=[ 10+5(？ √35)+? √ 1225)/60-I√3[5(？ √35)-? √ 1225]/60?

(3) Use the first coefficient of a letter to score the constant term.

(4) Check by the first coefficient of another letter.

(5) horizontal addition and vertical multiplication.

Extended data:

decomposition method

Factorial decomposition mainly includes cross multiplication, undetermined coefficient method, double cross multiplication, symmetric polynomial method, rotational symmetric polynomial method, remainder theorem method and so on. There is no universal method to find the root common factor decomposition. The junior high school mathematics textbooks mainly introduce the methods of putting forward common factors, using formulas and grouping decomposition. There are French division, addition and subtraction, method of substitution, long division, short division, division and so on.

Methods of improving common factor

If every term of a polynomial has a common factor, we can put forward this common factor, so that the polynomial can be transformed into the product of two factors. This method of decomposing factors is called the improved common factor method.

The common factor of each term is called the common factor of each term of this polynomial. The common factor can be a monomial or a polynomial.

Specific methods: Before determining the common factor, we should consider both the coefficient and the factor. When all the coefficients are integers, the coefficients of the common factor formula should take the greatest common divisor letter of each coefficient and the same letter of each letter, and the index of each letter should take the smallest number.

When the coefficient of each term has a score, the common factor coefficient is the greatest common divisor of each score. If the first term of the polynomial is negative, a negative sign should be put forward to make the coefficient of the first term in brackets become positive. When the negative sign is put forward, the term of the polynomial should be changed.

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