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### Grade 8 - Mathematics7.42 Problems - VI

 Example: If a+b+c = 6 and a2+b2+c2 = 26, find the value of ab+bc+ca. Solution: Given that a+b+c = 6 Squaring on both sides, we get (a+b+c)2 = 62 a2+b2+c2+2(ab+bc+ca) = 36 26+2(ab++bc+ca) = 36 2(ab+bc+ca) = 36-26 2(ab+bc+ca) = 10 ab+bc+ca = 10/2 ab+bc+ca = 5 Directions: Solve the following problems. Also write at least ten examples of your own.
 Q 1: If a+b+c = 10 and a2+b2+c2 = 56, find the value of ab+bc+ca.24222628 Q 2: If a+b+c = 6 and a2+b2+c2 = 20, find the value of ab+bc+ca.8101412 Q 3: If a+b+c = 12 and a2+b2+c2 = 88, find the value of ab+bc+ca.28262430 Q 4: If a+b+c = 9 and a2+b2+c2 = 45, find the value of ab+bc+ca.16182214 Q 5: If a+b+c = 7 and a2+b2+c2 = 29, find the value of ab+bc+ca.1410128 Q 6: If a+b+c = 5 and a2+b2+c2 = 21, find the value of ab+bc+ca.2846 Question 7: This question is available to subscribers only! Question 8: This question is available to subscribers only!