√28(√14-√7)-2√98=√4*√7(√7*√2-√7)-2*√2*√49=√2²*√7*√7(√2-1)-2*√2*√7²=2*√7²(√2-1)-2*7*√2=2*7*(√2-1)-14√2=14√2-14-14√2=-14
x + y = 49
- x + y = 17
------------------------ сложим ( + )
x - x + y + y = 49 + 17
2y = 66
y = 33
x = 49 - y = 49 - 33 = 16
<u>Ответ:</u>
( 16; 33)
Sin²t=1:(1+ctg²t)=1:(1+441/400)=1:841/400=400/841
sint=20/29
cost=-√(1-sin²t)=-√(1-400/841)=-√(441/841)=-21/29
tgt=sint/cost=20/29;(-21/29)=-20/29*29/21=-20/21
или tgt=1/ctgt=1:(-21/20)=-20/21
Расскрываем скобки 6,2a-3+<span>4-7,2a
6,2а-7.2а+(-3)+4
-1а+1</span>