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15a2+ab-6b2 =(?a+?b)(?a-?b) Factors of 15= 3 and 5 Factors of 6= 2 and 3 If we try (3a+2b)(5a-3b) that gives us 15a2+10ab-9ab-6b2 = 15a2+ab-6b2 therefore the answer is (3a+2b)(5a-3b)

5(x+4)-3(2+3x)

Expand first bracket 

5x+20-3(2+3x) 

Expand second bracket

5x+20-6-9x

simplify

14-4x

This involves the product rule for counting. Step 1: Identify the possible numbers for the first digit 5, 6, 7, 8 or 9 (5 in total) Step 2: Identify the possible numbers for the second digit 2, 3, 5 or 7 ...