Question 1079154
a) *[illustration DAs2.png].
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b){{{X=(16+2Y)(20+2Y)-16*20}}}
{{{X=(16+2Y)(20+2Y)-320}}}
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c) {{{(16+2Y)(20+2Y)-320=168}}}
{{{320+32Y+40Y+4Y^2-320=168}}}
{{{4Y^2+72Y-168=0}}}
{{{Y^2+18Y-42=0}}}
{{{(Y^2+18Y+81)-42=81}}}
{{{(Y+9)^2=123}}}
{{{Y+9=0 +- sqrt(123)}}}
{{{Y=-9 +- sqrt(123)}}}
Only the positive solution makes sense here,
{{{Y=sqrt(123)-9}}}{{{ft}}}