Вариант 9 1) 15х2 + 4 = 16х 2) 7х2 = 4х – 3 3) 2х – 5х2 = 0 4) 5х2 – 20 = 0 5) 7х + 3 + 4х2 = 0 6) х2 – 9х + 18 = 0 7) 16k2 + 9 – 24k = 0

15x²+4=16x
15x²-16x+4=0
D=16²-4*15*4=256-240=16
x=(16+4)/2*15=20/30=2/3
x=(16-4)/2*15=12/30=2/5

7x²=4x-3
7x²-4x+3=0
D=4²-4*7*3<0 => x∈∅

2x-5x²=0
x(2-5x)=0
x=0, 2-5x=0
x=0, 5x=2
x=0, x=0,4

5x²-20=0/:5
x²-4=0
x²=4
x=2, x=-2

7x+3+4x²=0
4x²+7x+3=0
a-b+c=0 (4-7+3=0) => x=-1, x=-3/4=-0,75

x²-9x+18=0
D=9²-4*18=81-72=9
x=(9+3)/2=12/2=6
x=(9-3)/2=6/2=3

16k²+9-24k=0
16k²-24k+9=0
D=24²-4*16*9=576-576=0
k=24/2*16=24/32=6/8=3/4=0,75

1)
15x² - 16x + 4 = 0
D = 256 - 240 = 16
x₁ = (16+4)/30 = 2/3
x₂ = (16-4)/30 = 0,4

2)
7x²- 4x + 3 = 0
D = 16 - 84 < 0
не имеет решений в действительных числах

3)
x(2 - 5x) = 0
x₁ = 0
x₂ = 0,4

4)
5x² - 20 = 0
x² = 4
x₁ = -2
x₂ = 2

5)
4x² + 7x + 3 = 0
D = 49 - 48 = 1
x₁ = (-7-1)/8 = -1
x₂ = (-7+1)/8 = -6/8 = -3/4 = -0,75

6)
x² - 9x + 18 = 0
D = 81 - 72 = 9
x₁ = (9-3)/2 = 3
x₂ = (9+3)/2 = 6

7)
16k² - 24k + 9 = 0
(4k - 3)² = 0
x = 3/4 = 0,75