Question

f: R-R ; f(x) = 2x+8. Calculati:

f(radical2 + 5) - f(radical2 -5)

Answer 1

f($\sqrt{2} + 5$) = $2( \sqrt{2} +5) + 8 = 2 \sqrt{2} + 10 + 8 = 2 \sqrt{2} + 18$

f($\sqrt{2} -5$) = $2( \sqrt{2} - 5) + 8 = 2 \sqrt{2} - 10 +8=2 \sqrt{2} -2$

f($\sqrt{2} + 5$) - f($\sqrt{2} -5$) = $2 \sqrt{2} +18 - 2 \sqrt{2} + 2 = 20$

Answer 2

2(√2+5)+8-(2(√2-5)+8)=2(√2+5-√2+5)+8-8=2*10=20