Solve this quadratic equation by completing the square. x2 + 10x = 26

x² + 10x = 26

x² + 10x + 25 = 26 + 25

x² + 5x + 5x + 25 = 51

x (x) + x (5) + 5 (x) + 5 (5) = 51

x (x + 5) + 5 (x + 5) = 51

(x + 5) (x + 5) = 51

(x + 5) ² = 51

x + 5 = ±√ (51)

- 5 - 5

x = - 5 ± √ (51)

x = - 5 + √ (51) or x = - 5 - √ (51)

Ax^2+bx+c=d

to comlete teh square

minus c to both sides

make sure a=1, if not, divide both sides by a

take 1/2 of b, then square that and add that to both sides

so

x^2+10x=26

c is already over

a=1

b=10

10/2=5

5^2=25

add 25 both sides

x^2+10x+25=26+25

factor

(x+5) ^2=51

sqrt both sides

x+5=+/-√51

minus 5

x=-5+/-√51

x=-5+√51 or - 5-√51