Question

if a+b=8 and ab=15÷4 find a-b = ?

Answer 1

Answer:

Step-by-step explanation:

a+b=8 and ab=15÷4

a-b=?

(a-b) ^2

(a-b) ^2=(a+b) ^2 - 4ab

(a-b) ^2=8^2-4.15/4

(a-b) ^2=64-15

(a-b) ^2=49

(a-b) =7

Hope it helps

Answer 2

Answer:

$\bold{\pm 7}$

Step-by-step explanation:

$\bold{To\ remember...} \\ \\ \\ If \ a + b = m\ \ \&\ \ \ ab = n, \\ \\ then \ a - b = \sqrt{m^2 - 4n}$

$\\ \\ \\ Here , \\ \\ m = 8\ \ ;\ \ n = \frac{15}{4} \\ \\ a - b \\ \\ = \sqrt{8^2 - (4 \times \frac{15}{4})} \\ \\ = \sqrt{64 - 15} \\ \\ = \sqrt{49} \\ \\ = \bold{\pm 7}$

$\\ \\ \\ \therefore\ a - b = \bold{\pm 7}$