## anonymous 4 years ago What is the length of side BC? A: 6 B: 21 C: 9 D: 15

1. anonymous

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2. anonymous

$a^{2}+b ^{2}=c ^{2}$ $15^{2}+\left( x+6 \right)^{2}=x ^{2}$ use foil

3. anonymous

those lines there mean that the two sides are congruent and x would be 15 and 15 plus 6 is 21 so the answer is 21.