Question

Решите уравнение (2-5х)^2=9 Помогите пожалуйста....

Answer 1

( 2 - 5x)^2 = 9
4 - 20x + 25x^2 - 9 =0
25x^2 - 20x - 5 = 0
5x^2 - 4x - 1 = 0
D = b^2 - 4ac = 16 + 20 = 36 = 6^2
x1 = ( 4 + 6) / 10 = 1
x2 = ( 4 - 6) / 10 = - 0,2

Answer 2

(2-5х)²=9; 4-20х+25х²=9; 25х²-20х-5=0; 5х²-4х-1=0; D=16-4×5×(-1)=36; х1=(4+6)/10=1; х2=(4-6)/10=0,2