LATIHAN SOAL FUNGSI KUADRAT

SOAL BERIKUT PENYELESAIAN

1.     y = x^2 – 25     

y = 0

0 = x^2 – 25

(x – 5) (x + 5 )

x = 5 x = -5

(5, 0) (-5, 0)

x = 0

y = 0^2 – 25

y = -25

(0, -25)

Xp     = - (b/2a)

          = -(0/2.1)

          = 0

Yp     = -(b^2 – 4ac/4a)

          = -(0^2 – 4.1.-25/4.1)

          = -(0+100/4)

          = -25

(0, -25)

2.     y = -x^2 + 7x – 12

y = 0

0 = x^2 + 7x – 12

(-x + 4 ) (x – 3)

x = 4 x = 3              

(4, 0) (3, 0)

x = 0

y = 0^2 +7(0) – 12

y = -12

(0, -12)

Xp     = -(b/2a)

          = -(7/2.-1)

          = -(7/-2)

          = 3,5

Yp     =-(b^2 – 4ac/4a)

          = -(7^2 – 4.-1.-12/4.-1)

          = -(49 – 48/-4)

          = -(1/-4)

          = 0,25

(3,5; 0,25)

3.     y = –x^2 – 8x + 9

y = 0

0 = -x^2 – 8x + 9

(-x – 9) (x – 1)

x = -9 x = 1

(-9, 0) (1, 0)

x = 0

y = -0^2 -8(0) + 9

y = 9

(0, 9)

Xp     = -(b/2a)

          = -(-8/2.(-1))

          = -4

Yp     = -(b^2 – 4ac/4a)

          = -(-8^2 – 4(-1).9)/4(-1))

          = -(64 + 36/-4)

          = - (-25)

          = 25

(-4, 25)

4.    

y = 0

(0,5; 0) (-4, 0)

x = 0

y = -2.0^2 – 7.0 + 4

y = 4

Xp     = -(b/2a)

          = -(-7/2.-2)

          =-(-7/-4)

          = - 1,75

Yp     = -(b^2 – 4ac/4a)

          =- (7^2 – 4.-2.4/4.-2)

          = -(49 + 32/-8)

          = -(-10,125)

          = 10,125

(-1,75; 10,125)

5.     y = -x^2 + 6x

y = 0

-x^2 + 6x

x(-x + 6) = 0

x = 0 x = 6

(0, 0) (6,0)

x = 0

y = 0^2 + 6(0)

y = 0

(0, 0)

Xp     = -(b/2a)

          = -(6/2.-1)

          = -(-3)

          = 3

Yp     = -(b^2 – 4ac/4a)

          = -(6^2 – 4.-1.0/4(-1))

          = -(36 – 0/-4)

          = -(-9)

          = 9

(3, 9)

 

 

 

 

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