Use the equation: the sum of 5 times of a number and 60% of the number is 56. What is the number?

Use the equation: the sum of 5 times of a number and 60% of the number is 56. What is the number?

Let this number be X
5x+60%x=56
5.6x=56
x=10
A: the number is 10

45% of a number is 56% more than 20% of 120. What's the number? The formula is______ ．

According to the meaning of the question, the formula is: (120 × 20% + 56) △ 45, so the answer is: (120 × 20% + 56) △ 45

Third order determinant linear equations, the first line x1-x2 = - A, the second line x2 + X3 = - B, the third line x1-x3 = - C

Equations (1), (2), (3) are called respectively
Equation (1) + (2) gives X1 + X3 = - a-b
When combined with (3), X1 = (- a-b-c) / 2; X3 = (- A-B + C) / 2
x2=x1+a=(a-b-c)/2

If X1 and X2 are the two roots of the equation 2x2 + 5x-1 = 0, find the following expressions: (1) (x1-1) (x2-1); (2) x2x1 + x1x2

According to the meaning of the question, we get X1 + x2 = - 52, x1x2 = - 12, (1) the original formula = x1x2 - (x1 + x2) + 1 = - 12 + 52 + 1 = 3; (2) the original formula = X12 + x22x1x2 = (x1 + x2) 2 − 2x1x2x1x2 = (− 52) 2 − 2 × (− 12) − 12 = - 292