X/3=-y/4
x+y=5
x=5-y
(5-y)/3=-(y/4)
(5-y)/3+y/4=0
4(5-y)/12+3y/12=0
(20-4y+3y)/12=0
(20-y)/12=0
y=20
x+20=5
x=5-20=-15
Ответ: x=-15 y=20
Задание: <span>Решить уравнение.
4х²-9=0
4х²=9
х²=
х= </span><span>±
х=</span><span>±
х₁=1,5
х₂= - 1,5
Проверим:
4*1,5² - 9 = 4*2,25-9=9-9=0
4* (-1,5)² - 9 = </span><span>4*2,25-9=9-9=0</span>
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<em>a</em>4<span> = </span><em>a</em>3<span> • </span><em>q</em><span> = (</span><em>a</em>1<span> • </span><em>q</em>2<span>) • </span><em>q</em><span> = </span><em>a</em>1<span> • </span><em>q</em>3