There are four functions as follows: ① y = 1 / X; ② y = - 1 / X; ③ y = X-1; ④ y = x + 1? A. ① and ② B. (2) and (3) C. (3) and (4) D. (2) and (4)

There are four functions as follows: ① y = 1 / X; ② y = - 1 / X; ③ y = X-1; ④ y = x + 1? A. ① and ② B. (2) and (3) C. (3) and (4) D. (2) and (4)

The answer is D, that is, there is a second quadrant for two and four

There is also a problem 1. If we know that the first-order function passes through (2,3) and forms a triangle with the coordinate axis in the first quadrant, we can find the minimum area of the triangle and prove it

The intercept formula shows that X / A + Y / b = 1
Again (2,3)
SO 2 / A + 3 / b = 1
S = 1 / 2Ab * (2 / A + 3 / b) * (2 / A + 3 / b) in order to construct the mean inequality, we multiply it twice
=6+2b/a+9a/2b≥6+2√9=12
So the minimum is 12

If the area of the triangle formed by the first-order function y = - 2x + m and two coordinate axes is 4, the value of M can be obtained
If clear and correct, I will add points!

Find the intersection of x-axis and y-axis first
One is the intercept greater than 0 above the x-axis
One is that the intercept is less than 0 below the x-axis
x=0 y=m
y=0 x=m/2
S=1/2|m*(m/2)|=4
So m = 4 or M = - 4
M = 4 intercept greater than 0 above X-axis
M = - 4, intercept less than 0, below the x-axis

The area of the triangle formed by the first-order function y = - 2x + m and the two coordinate axes is 4, and M is obtained

When x = 0, y = m, this is the length of one side of the triangle
When y = 0, x = m / 2, which is the length of the other side of the enclosed triangle
Then, the area of triangle is: [M * (M / 2)] / 2 = 4,
The solution is: M = ± 4