1) a^2 - 10a + 25 = (a - 5) ^2

2) 25 - a^2 = (5 + a) (a - 5)

3) (b - 1) (a - 5) = - (1 - b) (a - 5)

4) (a - 1) (2a - 5) = 2a^2 + 2a - 5

1) a^2 - 10a + 25 = (a - 5) ^2 (a - 5) ^2=a^2-10a+25

a^2-10a+25=a^2-10a+25

a^2-10a+25-a^2+10a-25=0

0=0

2) 25 - a^2 = (5 + a) (a - 5) 3) (b - 1) (a - 5) = - (1 - b) (a - 5)

25-a^2-5a+a^2+25a-5a=0 (b - 1) (a - 5) = (b+1) (a - 5)

15a+25=0 ba-a-5b-ba-a+5b+5=0

15a=-25 2a+5=0

a=-25/-15 2a=-5

a=5/3 a=-5/-2

a=2.5