Why can we calculate the limit when the denominator tends to zero Although by multiplying or dividing a number (both numerator and denominator) But in this case, is it still the original function?

Why can we calculate the limit when the denominator tends to zero Although by multiplying or dividing a number (both numerator and denominator) But in this case, is it still the original function?

For example, 1 / X (when x tends to 0) can only say that x is very close to 0, but x can not take 0. Because when x = 0, it is meaningless. When the numerator and denominator tend to 0, you can multiply the numerator and denominator by an East (non-zero) at the same time

If x tends to zero in the limit, the denominator cannot be zero
limx~0(tanx-sinx)/x ^3

Is 10x-10 = 0 an equation?

An integral equation with only one unknowns and one degree of unknowns is called univariate linear equation. The usual form is ax + B = 0 (a, B are constants, and a ≠ 0). 10x-10 = 0. It is univariate linear equation with unknown X and one degree of unknowns. 10x = 10
x=1
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Cos (a-pi / 2) / sin (5pi / 2 plus a) × sin (a-2pi) × cos (2pi-a)

Cos (a-pi / 2) / sin (5pi / 2 plus a) × sin (a-2pi) × cos (2pi-a)
=cos(π/2 - a)/sin(π/2 +a) ×sina×cos(-a)
=sina/cosa ×sina×cosa
=Sin squared a

There are 100 simple equations in grade five,
Without decimal fraction,

X-5.7=2.15 15 5X-2X=18 3X+0.7=5 3.5×2= 4.2+x 26×1.5= 2x+10 0.5×16―16×0.2=4x 13 9.25－X=0.403 16.9÷X=0.3 X÷0.5=2.6 x＋13＝33 3 － 5x＝80 1.8 +6x＝54 6.7x －60.3＝6.7 9 ＋4x ＝40

It is known that Tan α = 3
Find (1) sin α + cos α / sin α - cos α
（2）sinαcosα

Solution
(Sina + COSA) / (Sina COSA) -- numerator denominator divided by cosa at the same time
=(tana+1)/(tana-1)
=(3+1)/(3-1)
=2
sinacosa
=(sinacosa) / (Sin & # 178; a + cos & # 178; a) - the original formula divided by cos & # 178; a + Sin & # 178; a = 1
=(Tana) / (Tan & # 178; a + 1) - the numerator denominator is divided by cos & # 178; a at the same time
=3/(9+1)
=3/10

If P (- 2,4), PQ = 3, PQ is parallel to X axis, then the coordinate of point Q————

Parallel to the X axis, the ordinates are equal
-2+3=1
-2-3=-5
So Q (1,4) or (5,4)

What's four minus nine fourths,

4 is 16 out of 4. 16 out of 4 minus 9 out of 4 equals 7 out of 4

The equation of a line which is parallel to the line 2x + 3Y + 5 = 0 and whose sum of intercept on the two coordinate axes is 6 is______ ．

Suppose that the linear equation is 2x + 3Y + C = 0, let x = 0 get y = − C3, let y = 0 get x = − C2, ■ − C3 − C2 = 6, let C = − 365, let 2x + 3y-365 = 0, let x = 0 get y = − C3, let y = 0 get x = − C2, ■ − C3 − C2 = 6, let C = − 365, let 2x + 3y-365 = 0, let x = 0 get 10x + 15y-36 = 0, so the answer is: 10x + 15y-36 = 0

Calculation of 2 + 7 + 12 + 17 +. 192 + 197 with simple method
Help answer urgent need

2+7+12+17+.192+197
=2+12+22+32+.+192+7+17+27+.+197
=（2+192）*20/2+（7+197）*20/2
=194*10+204*10
=1940+2040
=3980