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[tex]$A$[/tex] is the point [tex]$(-5, 2)$[/tex]
[tex]$B$[/tex] is the point [tex]$(7, -2)$[/tex]
[tex]$C$[/tex] is the point [tex]$(-2, 5)$[/tex]

a) Find the gradient of a line perpendicular to line [tex]$AB$[/tex].
b) Find the equation of the line perpendicular to line [tex]$AB$[/tex] and passing through point [tex]$C$[/tex].

a) Gradient of the perpendicular line:
[tex]$\frac{1}{3}$[/tex]

b) Equation of the line:
[tex]$y = $[/tex]


Sagot :

Let's solve this step-by-step:

### Given Points:
- Point [tex]\( A = (-5, 2) \)[/tex]
- Point [tex]\( B = (7, -2) \)[/tex]
- Point [tex]\( C = (-2, 5) \)[/tex]

### Part (a): Find the Gradient of the Line Perpendicular to Line AB

1. Find the Gradient (Slope) of Line AB:
- The formula to calculate the slope between two points [tex]\((x_1, y_1)\)[/tex] and [tex]\((x_2, y_2)\)[/tex] is:
[tex]\[ \text{Slope}_{AB} = \frac{y_2 - y_1}{x_2 - x_1} \][/tex]

- Substituting the coordinates of points [tex]\( A \)[/tex] and [tex]\( B \)[/tex]:
[tex]\[ \text{Slope}_{AB} = \frac{-2 - 2}{7 - (-5)} = \frac{-4}{12} = -\frac{1}{3} \][/tex]

2. Find the Gradient of the Perpendicular Line:
- The slope of a line that is perpendicular to another line is the negative reciprocal of the original slope.
[tex]\[ \text{Slope}_{\text{perpendicular}} = -\frac{1}{\left(-\frac{1}{3}\right)} = 3 \][/tex]

- Thus, the gradient of the line perpendicular to line [tex]\( AB \)[/tex] is:
[tex]\[ \boxed{3} \][/tex]

### Part (b): Find the Equation of the Line Perpendicular to Line AB and Passing Through Point C

1. Use the Point-Slope Form of the Equation of a Line:
- The equation of a line in point-slope form is:
[tex]\[ y - y_1 = m(x - x_1) \][/tex]
where [tex]\((x_1, y_1)\)[/tex] is a point on the line and [tex]\( m \)[/tex] is the slope.

2. Substitute the Point [tex]\( C \)[/tex] and the Slope:
- Point [tex]\( C = (-2, 5) \)[/tex] and the perpendicular gradient [tex]\( m = 3 \)[/tex]:
[tex]\[ y - 5 = 3(x - (-2)) \][/tex]
- Simplify and solve for [tex]\( y \)[/tex]:
[tex]\[ y - 5 = 3(x + 2) \][/tex]
[tex]\[ y - 5 = 3x + 6 \][/tex]
[tex]\[ y = 3x + 6 + 5 \][/tex]
[tex]\[ y = 3x + 11 \][/tex]

- Thus, the equation of the line is:
[tex]\[ \boxed{y = 3x + 11} \][/tex]

To summarize:

- The gradient of the line perpendicular to line [tex]\( AB \)[/tex] is [tex]\( 3 \)[/tex].
- The equation of the line perpendicular to line [tex]\( AB \)[/tex] and passing through point [tex]\( C \)[/tex] is [tex]\( y = 3x + 11 \)[/tex].