What does it mean that function f (x) is defined at point x = x0? What does it mean that function f (x) is continuous at point x = x0?

What does it mean that function f (x) is defined at point x = x0? What does it mean that function f (x) is continuous at point x = x0?

The function f (x) is defined at the point x = x0, which means that f (x) is meaningful at x = x0 and belongs to the point in the domain of definition. F (x) is continuous at the point x = x0, which means that both left and right limits exist at the point x = x0 and are equal to f (x0)

(a+b)²-4（ab-10²

(a+b)²-4（ab-1)²
=(a+b+2ab-2)(a+b-2ab+2)

Because x squared equals x times x, X squared equals 2x

X squared equals x times x, 2x = x + X, so wrong
Or use the special case method, let x = 10, then x square = 100, 2x = x + x = 20

X △ 6 / 35 = 26 △ 13 / 25 to solve the equation

X÷(6/35)=26*(25/13)=50
X=50*(6/35)=60/7

Let a be a third-order matrix, A1, A2, A3 be column vectors and linearly independent, Aa1 = a1-a2 + 2A3, aa2 = a1 + A2 + 3a3, aa3 = - a1 + a2-3a3, find the determinant of A

A(a1,a2,a3)=C(a1,a2,a3)
C=
-1.2
  1.1.3
   -1.1.-3
|C|=-2*1=-2

(x + 3) × (x-7.5) = (x-3) &# 178; how to solve?

(x+3)×（x-7.5）=(x-3)²
x²-4.5x-22.5=x²-6x+9
(6-4.5)x=22.5+9
1.5x=31.5
x=21

A group of mutually unequal rational numbers x1, X2, X3, x4, X5 arranged from small to large, in which each number is less than - 1, then data 1, x1, - X2, X3,
-What is the order of X4 and X5 from small to large

LZ's score is really high, but I don't understand
I hope it can help you

If x ^ 2-2 (M-3) x + 16 is the complete square of X, then M =?

If x ^ 2-2 (M-3) x + 16 is the complete square of X
The results are as follows
2 (M-3) = 8, then the solution is m = 7
Or:
2 (M-3) = - 8, then the solution is: M = - 1
In conclusion, M = 7 or - 1

Triangle ABC, ad is the midline of BC side, e is the midpoint of AD, connecting be and extending AC to F, DG is the median line of triangle BCF
Verification: AF is half of FC, EF is one third of be

① ∵ DG is the median of △ BCF
∴DG‖BF FG=GC=1/2FC
And ∵ e is the midpoint of AD
F is the midpoint of Ag
Ψ EF is the median of △ ADG
∴AF=FG=1/2FC
② ∵ EF is the median of △ ADG
∴EF=1/2DG
∵ DG is the median of △ BCF
∴DG=1/2BF
∴EF=1/4BF
∴EF=1/3BE

2 to the power of 1999 plus 7 to the power of 1999

It is to find the last digit. 1 for 2, its end number of power 4N + 1 is 2, its end number of power 4N + 2 is 4, its end number of power 4N + 3 is 8, its end number of power 4N + 4 is 6, then it will cycle again. For 7, its end number of power 4N + 1 is 7, its end number of power 4N + 2 is 9, its end number of power 4N + 3 is 3, its end number of power 4N + 4 is 1, then