Math, asked by hprathore, 1 year ago

if a-b=7 & a^2+b^2=85 then find a^3-b^3​

Answers

Answered by harshita275
0

Answer:

a-b=7=>a=7+b.....(i)

a²+b²=85.....(ii)

substitution of equation 1 to equation 2.

(7+b)²+b²=85

49+14b+b²+b²=85

2b²+14b-36=0

b²+7b-18=0

(b+9)(b-2)=0

b=-9 v b=2

Find the value of a

a-b=7

=>if b=-9

a-(-9)=7

a=7-9

a=-2

=>if b=2

a=7+2

a=9

so value of a³-b³ there are 2 options

=>if (a,b) = (-2,-9)

a³-b³=-2³-(-9)³

= -8+729

= 721

=>if (a,b) = (2,9)

= a³-b³ = 2³-9³

= 8-729

= -721

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