Question

(iv) Which of the following equations has roots 3 and 5?
(A) x square + 3x + 5 = 0
(B) x square - 15x +8=0
(C) x square+ 8x - 15=0
(D) x square - 8x +15=0​

Answer 1

Answer:

Substitute 3 , 5 in each quadratic equation,

if it is true then 3 ,5 are roots of that equation.

i ) x² - 15x + 8 = 0

put x = 3 ,

3² - 15 × 3 + 8 = 0

9 - 45 + 8 = 0 ( false )

ii ) x² - 8x + 15 = 0

put x = 3

3² - 8 × 3 + 15 = 0

9 - 24 + 15 = 0

24 - 24 = 0 ( True )

put x = 5 , we get

5² - 8 × 5 + 15 = 0

25 - 40 + 15 = 0

40 - 40 = 0 ( true )

Therefore 3 , 5 are roots of x² - 8x + 15 = 0

Option ( B ) is correct.

I hope this helps you.

: )