20×29=580 (∵Positive x positve = Positive)
(−11)×7=−77 (∵Negative x positive = Negative) [1 mark] ∴20×29+(−11)×7=580−77=503 [1 mark]
Which of the following is the value of (√11−√7)(√11+√7)?
(a) -4
(b) 4
(c) √11
(d) √7