1.conducting experiments
1.conducting experiments 2.develop skill II
1.conducting experiments 2.develop skill II 3.with pleasure to do science
1.conducting experiments 2.develop skill II 3.with pleasure to do science 4.find out what's new in
1.conducting experiments 2.develop skill II 3.with pleasure to do science 4.find out what's new in 5. hold events
1.conducting experiments 2.develop skill II 3.with pleasure to do science 4.find out what's new in 5. hold events 6. Take a broad look at
1.conducting experiments 2.develop skill II 3.with pleasure to do science 4.find out what's new in 5. hold events 6. Take a broad look at 7.sharing talent
8.Speaking in public
8.Speaking in public 9.take a step forward
1.
а)х+7у=2 х+7у=2 8-у+7у=2 6у=-6 у=-1 х=9
х+у=8 х=8-у х=8-у х=8-у х=8+1 у=-1
б)2х+у=11 у=11-2х у=11-2х у=11-2*14 х=14
3х-у=4 3х-11-2х=4 х=14 х=14 у=-17
3.
а)3х-8у=6 * 6х-у=27 6х+27-6х=27 0х=0
3х+7у=21 у=-27-6х у=-27-6х у=-27
* 3х-8у+3х+7у=6+21
6х - у = 27
б)4х+5у=1 * 4х+5у=1 4х+5у=1
5х+7у=5 9х+12у=6 | : 3 ---> 3х+4у=2
* 4х+5у+5х+7у=1+5
9х+12у=6
х = 6 - 4а
6 - 4а > 0
-4a > -6
4a < 6
a < 1.5
ответ: уравнение имеет положительное решение при х ∈ (-∞; 1,5)