Question

For what value of r is the parallelogram a rhombus

Answer 1

9

Explanation:

7r+18=r²

r²-7r-18=0

factorizing

r²+2r-9r-18=0

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

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

r-9=0

r=9

check

(r²)=(9*9)=81

7r+18=7(9) + 8=81