Question

25x^2+90x+81=0
36x^2-84x+49=0

Answer 1

а²+2ав+в²=(а+в)²   а²-2ав+в²=(а-в)²
25х²+90х+81=0              36х²-84х+49=0
(5х+9)²=0                         (6х-7)²=0
0²=0
5х+9=0                              6х-7=0
5х=-9                                 6х=7
х=-9/5=-1,8                        х=7/6 = 1 1/7