Question

I need help

Solve each of these quadratic equations,
(a) x2 – 8x + 15 = 0
(c) 3x² + 10x + 7 = 0
(i) 2.x² + 9x = 0​

Answer 1

a) x =3 and x=5

c) x =-1 and
`x = (-7)/(3)`

i) x =0 and
`x = (-9)/(2)`

Explanation:

a)

Given that the quadratic equation

x² - 8x +15 =0

The factors of 15 = 5 × 3

x² - 5x -3x +15 =0

x(x -5) -3(x-5) =0

(x-3)(x-5) =0

x =3 and x=5

c)

3 x² + 10 x +7 =0

⇒ 3x² + 3x + 7x +7 =0

⇒ 3x (x +1) +7(x+1) =0

⇒ (x+1) ( 3 x +7) =0

⇒ x =-1 and
`x = (-7)/(3)`

i)

2 x ² + 9 x =0

⇒ x( 2 x + 9) =0

⇒ x =0 and 2 x = -9

⇒ x =0 and
`x = (-9)/(2)`