Jawaban:

1) (4,-3),dan titik (2,5)

y - y1 = x -x1

_____ _____

y2 -y1 x2 -x1

y - (-3) = x - 4

_____ ____

5 -(-3) 2 -4

y + 3 = x - 4

_____ ____

5 +3 2 -4

y + 3 = x - 4

_____ ____

8 -2

-2(y+3) = 8(x-4)

-2y -6 = 8x -32

-8x -2y -6 +32

-8x -2y +26 = 0

atau : 8x +2y -26 = 0

2) 2×+3y=5

m = -a = -2

___ ___

b 3

tegak lurus m lawan dan kebalikan

maka m (gradien) = 3

___

2

y - y1 = m (x - x1)

y - 1 = 3 (x -2)

___

2

2( y - 1) = 3( x -2)

2y -2 = 3x -6

-3x +2y -2 +6 = 0

-3x +2y +4 = 0

atau : 3x -2y -4 = 0

3) eliminasi x:

2x-4y=6 | x 3

3x+y=2 | x 2

6x -12y = 18

6x + 2y = 4

___________-

-14y = 14

y = 14 : -14

y = -1

eliminasi y:

2x-4y=6 | x 1

3x+y=2 | x 4

2x- 4y =6

12x+4y= 8

_________+

14x = 14

x = 14 : 14

x = 1

maka nilai -3x+2y = -3(1) +2(-1)

= -3 -2 = -5

4)-2y-3x=2 dan x+3y=-3

eliminasi x :

-3x -2y =2 |x 1

x+3y=-3 |-3

-3x - 2y = 2

-3x -9y = 9

___________-

7y = -7

y = -7 : 7

y = -1

eliminasi y

-3x -2y =2 |x 3

x+3y=-3 |-2

-9x -6y = 6

-2x -6y = 6

___________-

-7x = 0

x = 0 : -7

x =0

maka nilai dari -x-3y = -(0) -3(-1) = 0 +3 = 3

5)f(x)=ax²+7

f(1 ) = a (1)² + 7 =3

= a + 7 = 3

a = 3 -7

a = -4

f(x) = -4x² +7

f(-5) = -4(-5)² + 7

= -4(25) +7

= -100 +7

= -93