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Find the value of 2.7 ³ - 1.6 ³ - 1.1 ³ using a suitable identity.

User JuniKim
by
5.8k points

1 Answer

4 votes

Answer:

14.256

See details below

Explanation:

2.7 ³ - 1.6 ³ - 1.1 ³

= (2.7 ³ - 1.1 ³) - 1.6 ³ expand difference of two cubes

= (2.7 - 1.1)*(2.7^2 + 2.7*1.1 + 1.1^2) - 1.6 ³

= 1.6*(2.7^2 + 2.7*1.1 + 1.1^2) - 1.6 ³ factor out 1.6

= 1.6*(2.7^2 - 1.6^2 + 2.7*1.1 + 1.1^2) expand difference of two squares

= 1.6*( (2.7 - 1.6)*(2.7 + 1.6) + 2.7*1.1 + 1.1^2)

= 1.6*( 1.1*4.3 + 2.7*1.1 + 1.1^2) factor out 1.1

= 1.6*1.1* ( 4.3 + 2.7 + 1.1)

= 1.6*1.1*8.1 rearrange

= 1.6 * 8.1 * 1.,1

= 16 * 0.81 * 1.1

= (4*0.9)^2 * 1.1

= 3.6^2 * 1.1

= 12.96 * 1.1 36*36=1296

= 14.256

(to multiply by 1.1, mentally start from the right, add the left digit, carry if necessary)

User Akia
by
6.2k points
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