Question

q 21,22,23 answer pls pls ​

Answer 1

21)x-3=0

X=3

x^3+2x^2+Kx+3=21

(3)^3+2(3)^2+3k+3=21

27+18+3k+3=21

3k=-21+21-27

3k=-27

k=-9

x^3+2x^2+Kx-18

27+18+3*-9-18

27+18-27-18

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Answer 2

(1/a+1/b) can be written as( a+b)/ ab by taking the LCM so the second part now becomes{(a+b)/ab } - 2 ab

we have ab=4 and a+b =-5 Now simply substitute {-5/4}-2X4

=(-5/4)-8=-(37/4) will be the answer.

another way is also there, we can easily  calculate  a and b as -4 and -1.  Now substitute this to the equation (1/a + 1/b) –2a b 

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