Ответ:
1-ұшақ – 0,75х км/сағ
2-ұшақ – х км/сағ
2 сағ кейін: 2х 2000км
1-ұшақ – 1,5х км/сағ
2-ұшақ – 2х км/сағ
1,5х
П.т.б.: 2,25х2+4х2=4000000
6,25х2=4000000
х2=640000
х=800 (км/сағ)
Жауабы: 600км/сағ, 800км/сағ
<u>939. a)</u>(x-2)(x+3)=x(2-x)
x^2+3x-2x-6=2x-x^2
x^2+3x-2x-6-2x+x^2=0
2x^2-x-6=0
Д=(-1)^2-4*1*(-6)=1+24=25
x1=1.5
x2=-1
<u>б)</u>x(2x+1)=(2x+1)^2
2x^2+x=4x^2+4x+1
2x^2+x-4x^2-4x-1=0
-2x^2-3x-1=0
Д=(-3)^2-4*(-2)*(-1)=9-8=1
x1=-1
x2=-0.5
<u>в)</u>5(9-x^2)=x(x-3)
45-5x^2=x^2-3x
-5x^2-x^2+3x+45=0
-6x^2+3x+45=0
Д=3^2-4*(-6)*45=9+1080=1089
x1=3
x2=-2.5
<u>г)</u><u />2x(x+1)=x^2-1
2x^2+2x=x^2-1
2x^2-x^2+2x+1=0
x^2+2x+1=0
Д=2^2-4*1*1=0
x1/2=-1
3sin²2x+sin2x=sin²x-2sinxcosx+cos²x
3sin²2x+sin2x=1-sin2x
3sin²2x+sin2x-1+sin2x=0
3sin²2x+2sin2x-1=0
sin2x=a
3a²+2a-1=0
D=4+12=16
a1=(-2-4)/6=-1⇒sin2x=-1⇒2x=-π/2+2πn⇒x=-π/4+πn
a2=(-2+4)/6=1/3⇒sin2x=1/3⇒2x=(-1)^n*arcsin1/3+πn⇒x=(-1)^n*1/2arcsin1/3+πn/2
3х + 12 + х = -4
4х + 12 = -4
4х = -12 - 4 = -16
<u>х = -16 : 4 = -4
</u>3×(-4)+12-4=-4
<em>
Ответ: -4.</em>