How do you simplify #7a^2 - 2a^2#?

1 Answer
Alan P.
Nov 3, 2015

#7a^2-2a^2 = 5a^2#

Explanation:

Suppose you have square sheets of material; each sheet is identical to every other sheet and each sheet has dots arranged in a rectangular grid of #a# rows and #a# columns. There are #axxa =a^2# dots on each sheet of material.

Suppose you start the day with #7# such sheets of material; you start with #7xxa^2# or more simply #7a^2# dots.

If during the day you lose #2# of those sheets of material, you will have lost #2xxa^2# or #2a^2# dots.

During the day, #7# sheets minus #2# sheets becomes #5# sheets
#color(white)("XXX")7" sheets" - 2" sheets" = 5" sheets"#
and #7xxa^2# dots minus #2xxa^2# dots becomes #5xxa^2# dots
#color(white)("XXX")7a^2-2a^2=5a^2#

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