1 неверно
2 неверно
3 тоже не верно
4 верно
16х²-24х+9+9х²+12х+4=47-3х
25х²-12х+13=47-3х
25х²-12х+13-47+3х=0
25х²-9х-34=0
Д=-9²-4*25*(-34)=3481
х=9±59/50
х=9+59/50=34/25
х=9-59/50=-1
Ответ х1=-1 , х2=34/25
1)
(38²-28²): (47²-19²)=(38-28)(38+28) : (47-19)(47+19)=10*66 / 28*66 =10/28=5/24
2)
(53²-25²) : (79²-51²)=(53-25)(53+25) : (79-51)(79+51)=28*78/28*130=39/65
3)
(181²-61²) : (219²-77²)= (181-61)(181+61) : (219-77)(219+77)=120*242/142*296=
=15*121/71*37=1815/2627
4)
(200²-380²) : (420²-160²)= (200-380)(200+380) : (420-160)(420+160)= -180*580/260*580=-18/26=-9/13