Question

If a + b = 1 and a - b = 7, findi) ab ii) a2 + b2
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Answer 1

=>

(a+b)^2=a^2+b^2+2ab. ...(i)

=>

(a-b)^2=a^2+b^2-2ab ...(ii)

Adding (i) and (ii)

=>(a+b)^2+

(a-b)^2=2(a2+b2)+2ab-2ab

=>1^2+7^2=2(a2+b2)

=>1+49=2(a2+b2)

=>50/2=(a2+b2)

.˙.(a2+b2)=25

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Answer 2

Step-by-step explanation:

a+b=1.............1

a-b=7.............2

from 2

a=7+b

so in eq 1

7+b+b=1

2b=-6

b=-3

so

a=7+(-3)

a=4

so

i)ab

=4*(-3)

=-12

ii)a²+b²

4²+(-3)²

=16+9

=25

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