Question

a-b=7, ab=23.75,then a+b=

Answer 1

a-b=7
squaring both sides
a²+b²-2ab=49
add 4ab both sides
a²+b²+2ab=49+4ab
(a+b)²=49+4(23.75)
(a+b)²=49+95
(a+b)²=(144)
a+b=12

Answer 2

we know that,
a-b=7
squaring both sides, we get,
(a-b)²=49

we also know that
(a-b)²=(a+b)²-4ab
therefore,

(a+b)²-4ab=49
(a+b)²=49 + 4 * 23.75 [given]

(a+b)²=144

a+b=12