1
{2*7^x-3y=5⇒4^x=(3y+5)/2
{21/49*7^x-4y=-9⇒3/14*(3y+5)/2-4y=-9
9y+15-56y=-153
-47y=-153-15
47y=168
y=4
7^x=(12+5)/2=8,5
x=log(7)8,5
Ответ (log(7)8,5;4)
2
2^x=a
4a²-(4√2+1)a+√2≤0
D=(4√2+1)²-16√2=32+8√2+1-16√2=32-8√2+1=(4√2-1)²
√D=4√2-1
a1=(4√2+1-4√2+1)/2=1⇒2^x=1⇒x=0
a2=(4√2+1+4√2-1)/2=4√2⇒2^x=4√2⇒x=2,5
x∈[0;2,5]