Question
when x =5 and y =-7 then find the value of 27x³ +58x²y
+31xy² +8y³?Solution
27x³ +58x²y +31xy² +8y³ =27x³ +54x²y + 4x²y +36xy²-5 xy² +8y³ =(3x+2x) ³ +4x²y -5 xy² =[3×5+2×(-7)]³ + 4×25×(-7)-5×5×49 =1-700-1225 =1-1925 = -1924
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