Question

(x+5)²-(x+5)(x-5) = 20

Answer 1

(x+5)²-(x+5)(x-5) = 20

⇔x²+10x+25-x²-25=20

⇔10x=20

⇔x=2

Answer 2

\(\left(x+5\right)^2-\left(x+5\right)\left(x-5\right)=20\)

\(\Leftrightarrow\)\(\left(x+5\right)\left[\left(x+5\right)-\left(x-5\right)\right]=20\)

\(\Leftrightarrow\left(x+5\right)\left[x+5-x+5\right]=20\)

\(\Leftrightarrow\left(x+5\right).10=20\)

\(\Leftrightarrow\)\(x+5=2\Rightarrow x=-3\)

Answer 3

(x+5)²-(x+5)(x-5) = 20

(x+5)²-(x+5)(x-5)-20=0

(x+5)-(x+5-x+5-20)=0

(x+5)-(2x-10)=0

x+5=0 hoặc 2x-10=0

x=-5 2x=10

x=5