7x^2 - 4 = 0
7x^2 = 4
4
x^2 = ------ / : V
7
x = V4/7
x = - 2/V7 i x = 2V7
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проверим, верно ли
7 *(2V7)^2 - 4 = 0
4
7 *--------- - 4 = 0
7
верно
5-3x=3x-2
-3x-3x=-2-5
-6x=-7
x=7/6=1 1/6
y=5-3*7/6=5-3.5=1.5
(1 1/6;1.5)
3 ^ ( x + 1 ) * 2 ^ x = 108
3 ^ x * 3 * 2 ^ x = 108
6 ^ x = 108 : 3
6 ^ x = 36
6 ^ x = 6 ^ 2
x = 2
5Х-7У при x= 1/5, У= 2/21
<span>5*(1/5)-7*(2/21)=1-2/3=1\3</span>