i dont understand it

a

Step-by-step explanation:

A perpendicular bisector, intersects a line at its mid point and is perpendicular to it.

Calculate slope m using the slope formula

m =

with (x₁, y₁ ) = (- 7, 1) and (x₂, y₂ ) = (9, 13)

m = = = =

Given a line with slope m then the slope of a line perpendicular to it is

= - = - = - ←  slope of perpendicular bisector

Given endpoints (x₁, y₁ ) and (x₂, y₂ ) then the midpoint is

(, )

using (x₁, y₁ ) = (- 7, 1) and (x₂, y₂ ) = (9, 13) , then

midpoint = ( , ) = ( , ) = (1, 7 )

The equation of a line in slope- intercept form is

y = mx + c ( m is the slope and c the y- intercept )

Here m = - , then

y = - x + c ← is the partial equation

To find c substitute the midpoint (1, 7) into the partial equation

7 = - + c ⇒ c = + =

y = - x + ← equation of perpendicular bisector

7! = 7×6×5×4×3×2

3! = 3× 2

as 7! is multiple of 3! because 7! contains 3! that is 3× 2 as factor

so 7! /(3! ) = 7× 6× 5× 4

= 42 × 20

= 840

its b) 840✌✌✌

dhruv⭐