Question

If a-b=7 and ab=18 find a+b

Answer 1

Answer:

(a+b) = 11

Step-by-step explanation:

U can find the answer by this formula :

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

Answer 2

a - b = 7 -----(1)

ab = 18 ------(2) => a = 18/b -----(a)

using (a) in (1);

18/b - b = 7

18 - b^2 = 7b

b^2 +7b -18 = 0

=> $\fbox{b = -9}$ or $\fbox{b = 2}$

Now, when b = - 9, then:

a + 9 = 7

=>$\fbox{ a = -2}$

and when b = 2, then:

a - 2 = 7

=> $\fbox{a = 9}$

Now,

When a = -2 and b = -9, then:

★ a + b = -2 -9 = -11

and, When a = 7 and b = 2, then:

★ a + b = 2 + 9 = 11