0,3х - х2 = 0. 12 - 17х - 5х2 = 0. 7х - 4х2 = -15.. Created by kudryawtsewanas. algebra-ru

0,3х - х2 = 0. 12 - 17х - 5х2 = 0. 7х

Каришка2001 1) 0,3х-х2=0
х(0,3-х)=0
х=0 или 0,3 - х=0
х= -0,3
2) 12-17х-5х2=0
-5х2-17х+12=0 / (-1)
5х2+17х-12=0
Дискриминант = (17)2 - 4*5*(-12)=289+240=529
х1/2 = -17+-23/2 = 3 и -20
3) -4х2+7х+15=0 / (-1)
4х2-7х-15=0
Д= 49-4*(-15)*4=(решишь)
х1/2 = 7+-√Д / 2 = (решишь)
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надеюсь всё понятно

0 votes Thanks 0

dinarkaik $a) 0,3- x^{2} =0 \\ - x^{2} +0,3x=0 \\ x(-x+0,3)=0 \\ x=0,-x+0,3=0 =>x=0,3 \\ 
b) 12-17x-5 x^{2} =0 \\ -5 x^{2} -17x+12=0 \\ 5 x^{2} +17x-12=0 \\ D=17^{2}+4*12*5=23^{2} \\ x_{1} = \frac{-17+23}{2*5}=0,6; x_{2} = \frac{-17-23}{2*5}=-4 \\ 
c) 7x-4 x^{2} =-15 \\ 4 x^{2} -7x-15=0 \\ D=7^{2}+4*15*4=17^{2} \\ x_{1} = \frac{7-17}{2*4}= -\frac{10}{8}=-1,25; x_{2} = \frac{7+17}{2*4} =3$

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